effective maxillary protraction: hyrax expansion appliance

Graduate Theses, Dissertations, and Problem Reports

2009

Effective maxillary protraction: Hyrax expansion appliance vs. Effective maxillary protraction: Hyrax expansion appliance vs.

double-hinged expansion appliance double-hinged expansion appliance

Thuy B. Do-deLatour West Virginia University

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Effective Maxillary Protraction: Hyrax Expansion Appliance vs. Double-hinged Expansion Appliance

Thuy B. Do-deLatour, DMD

Thesis submitted to the School of Dentistry at West Virginia University

in partial fulfillment of the requirements for the degree of

Master of Science in

Orthodontics

Peter Ngan, D.M.D., Chairman Chris Martin, D.D.S, M.S.

Thomas Razmus, D.D.S., M.S.

Department of Orthodontics

Morgantown, WV 2009

Keywords: maxillary protraction, double-hinged expander, hyrax expander, Alt-RAMEC

ABSTRACT

Effective Maxillary Protraction: Hyrax Expansion Appliance vs. Double-hinged Expansion Appliance

Thuy B. Do-deLatour, DMD

Patients with a skeletal Class III malocclusion may have one of the following conditions: midface deficiency and/or mandibular hypertrophy/prognathism. If modification of the skeletal Class III growth pattern is not effectively accomplished at an early age via maxillary protraction, then orthognathic surgery would be required to help correct the skeletal Class III malocclusion. Some of the more serious risks associated with orthognathic surgery include parasthesia, bone and tissue necrosis, and possibly death. However, if one is able to effectively protract the maxilla, the need for anterior-posterior correction of the maxilla via orthognathic surgery will be minimized if not eliminated.

The purpose of this pilot study was to evaluate the quantitative difference, if any, between the conventional protraction technique using a one-time expansion and comparing it to a protraction protocol with the double-hinged expander as advocated by Liou.1-3 The differences between the two techniques were evaluated on lateral cephalometric radiographs, in which the skeletal and dental changes with maxillary expansion and protraction were measured.

The results of this study found that both treatment groups experienced statistically significant sagittal changes as compared to the control group. But the primary reason for the improvement of the Class III malocclusion is related to the downward and backward rotation of the mandible. The Hyrax expansion group had more “A” point forward movement; however, the success may have been attributed to the higher level of compliance in this group compared to the Double-hinged expansion group. Future studies reviewing the length of time that protraction forces are placed on the maxilla can help to clarify the results of protraction facemask therapy. Finally, more long-term studies are needed in order to evaluate the stability of the immediate success of maxillary expansion and protraction facemask therapy.

iii

DEDICATION This thesis is dedicated to my family who have sacrificed so much for me to get to where I am today. To my mother: Thank you for your unconditional love. You have sacrificed so much in order for me to have all that you did not have while growing up. Thank you for your dedication to helping me succeed and for taking care of my children. Because of your words of encouragement and your belief in me, I was able to achieve more than I thought was possible. I love you and will miss you always. To my husband: Thank you for your loving support all of these years. You are my best friend and the best husband and father there is. Few men would be able to make the sacrifices that you have made. Thank you for taking such great care of me and helping me to attaining my career goals. To my children: Thank you for your love and for making me so happy and blessed. You both are the love of my life.

iv

ACKNOWLEDGEMENTS A special thanks are extended to the following individuals: Dr. Peter Ngan for your kindness and generosity and for your mentorship. Dr. Chris Martin for always being there to help me out. Dr. Thomas Razmus for kindly serving as a member of my thesis committee. Dr. Erdrogan Gunel for putting up with me and generating all of the statistics. Rajia Sebbahi for your friendship and pep-talks. Kolin and family for your friendship and morning commutes. Michael Becht for being a great classmate. The Residents for all of the great memories.

v

CONTENTS

CHAPTER I INTRODUCTION ......................................................................................... 1

BACKGROUND ............................................................................................................ 1

STATEMENT OF THE PROBLEM .............................................................................. 2

SIGNIFICANCE OF THE PROBLEM .......................................................................... 2

NULL HYPOTHESIS .................................................................................................... 3

DEFINITION OF TERMS ............................................................................................. 3

ASSUMPTIONS ............................................................................................................. 5

LIMITATIONS ............................................................................................................... 5

DELIMITATIONS ......................................................................................................... 5

CHAPTER II LITERATURE REVIEW ............................................................................ 6

PREVALENCE OF CLASS III MALOCCLUSION ..................................................... 6

MORPHOLOGIC CHARACTERISTICS OF CLASS III MALOCCLUSION ............ 7

ETIOLOGY .................................................................................................................... 8

SKELETAL CLASS III GROWTH. .............................................................................. 9

Cranial Base Growth. .................................................................................................. 9

Nasomaxillary Complex. .......................................................................................... 10

Mandible ................................................................................................................... 12

DIAGNOSIS OF CLASS III MALOCCLUSION ........................................................ 12

TREATMENT OF CLASS III MALOCCLUSION ..................................................... 14

Growing patient. ....................................................................................................... 14

Non-growing patient ................................................................................................. 17

Methods of Early Treatment of Class III Malocclusion ........................................... 18

CHAPTER III MATERIALS AND METHODS ............................................................ 32

SAMPLE DESCRIPTION ............................................................................................ 32

RESEARCH DESIGN .................................................................................................. 35

Appliance Design and Expansion Protocol ............................................................... 35

METHODOLOGY ....................................................................................................... 39

Reliability of Cephalometric Measurements ............................................................ 40

Cephalometric Landmarks and Reference Planes ..................................................... 41

Measuring Procedure for Sagittal Changes. .............................................................. 43

Measuring Procedure for Vertical Changes. ............................................................. 44

Measuring Procedure for Angular Changes. ............................................................. 45

Evaluation of Overjet and Molar Relationship Correction ....................................... 46

vi

STATISTICAL TREATMENT .................................................................................... 47

EQUIPMENT AND MATERIALS .............................................................................. 48

CHAPTER IV RESULTS AND DISCUSSION .............................................................. 49

RESULTS ..................................................................................................................... 49


Statistical Significance Within the Treated Group ................................................... 53

Statistical Significance Within the Control Group ................................................... 59

Comparison of Treated and Control Groups ............................................................. 62

DISCUSSION ............................................................................................................... 71


Comparison of All Groups ........................................................................................ 71

Clinical Relevance. ................................................................................................... 79

CHAPTER V SUMMARY ............................................................................................... 82 REFERENCES ................................................................................................................. 83 APPENDICES .................................................................................................................. 91

Appendix A ................................................................................................................... 92

Appendix B ................................................................................................................... 93

Appendix C ................................................................................................................... 94

Appendix D ................................................................................................................... 95

Appendix E ................................................................................................................... 96

Appendix F.................................................................................................................... 97

Appendix G ................................................................................................................... 98

Appendix H ................................................................................................................... 99

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LIST OF TABLES

Table 1. Reported Incidence of Class III Malocclusion. ...............................................7

Table 2. Prevalence of Maxillary and Mandibular Anterior-Posterior Deficiency .......8

Table 3. Maxillary Length Changes. ...........................................................................11

Table 4. Positive and Negative Factors Influencing the Decision for Early Treatment ............................................................................................14

Table 5. Symbols for the Different Time Intervals. ....................................................32

Table 6. Chronologic Age Distribution of Treatment and Control Samples ..............33

Table 7. CVM of Treatment and Control Samples .....................................................34

Table 8. The Seventeen Skeletal and Dental Landmarks. ...........................................42

Table 9. Definition of the Reference Lines. ................................................................42

Table 10. The Sagittal Measurements of Variables (1-9) .............................................44

Table 11. The Vertical Measurements of Variables (10-16) ........................................45

Table 12. The Angular Measurements of Variables (17-24) ........................................46

Table 13. Calculation of Overjet and Molar Relationship Changes. ............................46

Table 14. Intraclass Correlation Coefficient of Reliability for Sagittal, Vertical, Angular Measurements, and Superimpositions ...............51

Table 15. Sagittal Measurements at T1 and T2 in the Double-hinged Expander Group ...................................................................53

Table 16. Vertical Measurements at T1 and T2 in the Double-hinged Expander Group ...................................................................54

Table 17. Angular Measurements at T1 and T2 in the Double-hinged Expander Group ...................................................................55

Table 18. Sagittal Measurements at T1 and T2 in the Hyrax Expander Group .................................................................................56

Table 19. Vertical Measurements at T1 and T2 in the Hyrax Expander Group .................................................................................57

Table 20. Angular Measurements at T1 and T2 in the Hyrax Expander Group .................................................................................58

Table 21. Sagittal Measurements at t1 and t2 for the Control Group ...........................60

Table 22. Vertical Measurements at t1 and t2 in Control Group ..................................61

Table 23. Angular Measurements at t1 and t2 in Control Group ..................................62

Table 24. Comparison of the Mean Difference Among all Groups ..............................63

Table 25. Mean Change in SNA Following Protraction Facemask Therapy................78

viii

LIST OF FIGURES

Figure 1. Hyrax Expander with Protraction Hooks ......................................................36

Figure 2. Double-Hinged Expander with Protraction Hooks .......................................36

Figure 3. Protraction Facemask ....................................................................................38

Figure 5. The Skeletal and Dental Landmarks .............................................................41

Figure 6. The Reference Grid (Ols and Olp) and Measuring Points Used in the Sagittal Cephalometric Analysis. ..................................................................43

Figure 7. The Reference Lines and Measuring Points Used in the Vertical Cephalometric Analysis ..................................................................44

Figure 8. The Reference Lines and Measuring Points Used for the Angular Cephalometric Analysis ..................................................................45

Figure 9. Total Observation (Double Hinged): Sagittal Changes ................................67

Figure 10. Total Observation (Hyrax): Sagittal Changes ...............................................67

Figure 11. Total Observation (Double Hinged): Vertical and Angular Changes ...........69

Figure 12. Total Observation (Hyrax): Vertical and Angular Changes .........................69

1

CHAPTER I

INTRODUCTION

BACKGROUND

Patients having a Class III malocclusion may present with an anterior crossbite

and/or a Class III molar relationship. Proclination of mandibular incisors and

retroclination of maxillary incisors can cause posturing of the mandible in an anterior

position due to incisal interference. This is a condition known as pseudo-Class III

malocclusion and is really a Class I malocclusion. Individuals with a true skeletal Class

III malocclusion present with one of the following conditions: midface deficiency and/or

mandibular hypertrophy/prognathism.4 It has been reported that a significant percentage

of the skeletal Class III malocclusion cases are due to maxillary retrusion5,6. The

incidence of Class III malocclusion among American children is about 1% and is slightly

higher in youths and adults7; whereas, the prevalence of Class III malocclusion in the

Chinese and Japanese populations has been found to be as high as 14%.8,9 The etiology

of Class III malocclusion can be genetic or environmental.

Early treatment using protraction facemask therapy in conjunction with rapid

maxillary expansion appliance has been shown to be successful in correcting skeletal

Class III malocclusions that are due primarily to deficient maxillary development.10-12

Rapid maxillary expansion is used to disarticulate the maxilla from the surrounding bones

which are connected by circum-maxillary sutures.2 The goal of combining the rapid

maxillary expansion appliance with the protraction face-mask is to provide a more

effective protraction of the maxilla.13-16 However, studies have shown that the average

2

amount of maxillary protraction is only about 1.5mm - 3mm over a period of 8-12

months.17-19 Furthermore, the circum-maxillary sutures start to interlock or interdigitate

during pubertal growth spurt making it difficult to protract in older patients. 20 Liou et al.2

reported the use of a double-hinged expander as having a center of rotation around the

tuberosity, which differs from the conventional Hyrax expander; therefore, the double-

hinged expander will give a more forward movement of the maxilla during expansion. In

addition, the repeated expansion and contraction of the maxilla seems to help in

loosening the circum-maxillary sutures, allowing a more effective forward movement of

the maxilla during protraction.

The purpose of this study is to evaluate the quantitative difference, if any,

between the conventional protraction technique using the traditional Hyrax expander and

the new protraction protocol with the double-hinged expander as advocated by Liou. The

differences between the two techniques will be evaluated on lateral cephalometric

radiographs, in which the skeletal and dental changes with maxillary expansion and

protraction will be measured.

STATEMENT OF THE PROBLEM

Can multiple expansion and contraction of the maxilla using the double-hinged

expander lead to a more effective protraction of the maxilla as compared to a one-time

expansion technique using the Hyrax expander?

SIGNIFICANCE OF THE PROBLEM

A patient with a skeletal Class III malocclusion may have one of the following

conditions: midface deficiency and/or mandibular hypertrophy/prognathism. If

modification of the skeletal Class III growth pattern is not effectively accomplished at an

3

early age via maxillary protraction, then the patient will require orthognathic surgery in

order to correct his/her skeletal Class III malocclusion. Some of the more serious risks

associated with orthognathic surgery include parasthesia, bone and tissue necrosis, and

possibly death. However, if one is able to effectively protract the maxilla, then the need

for anterior-posterior correction of the maxilla via orthognathic surgery will be

minimized if not eliminated.

NULL HYPOTHESIS

No significant difference in the skeletal and dental changes when comparing one-

time expansion using Hyrax expander and multiple expansion and constriction using a

Double-hinged expander for maxillary protraction.

DEFINITION OF TERMS

1. Prognathic: Forward relationship of the mandible relative to the craniofacial

skeleton.

2. Retrusion: Teeth and/or jaw posterior to their normal positions.

3. Facial concavity: A term applied to the analysis of a profile. The shape is described

as an inwardly rounded curve from the forehead to the lips to the chin. A concave

facial profile is often associated with a Class III malocclusion.

4. Class III malocclusion: Mesial (anterior) relationship of the lower first molar to the

upper, a retruded relationship of the upper first molar to the lower, or a combination

of the two. The mesiobuccal cusp of the upper first molar will typically occlude near

the embrasure between the lower first and second molars. Also, a patient with a

skeletal Class III malocclusion may have one of the following conditions: midface

deficiency and/or mandibular hypertrophy/prognathism.

4

5. Pseudo-Class III malocclusion: Proclination of mandibular incisors and

retroclination of maxillary incisors can cause posturing of the mandible in an anterior

position due to incisal interference.

6. Overbite: Vertical overlapping of upper teeth over lower teeth, usually measured

perpendicular to occlusal plane.

7. Overjet: Horizontal projection of upper teeth beyond the lower teeth, usually

measured parallel to the occlusal plane.

8. Rapid maxillary (palatal) expansion: Orthopedic widening of the two halves of the

maxilla using the high load system.

9. Protraction facemask: An extra-oral protraction appliance used to exert a forward

vector of force on the maxilla; for example, in maxillary deficiency problems.

10. Hyrax expander: This is the more commonly used type of banded rapid maxillary

expansion appliance. Bands are placed on the maxillary first molars and first

premolars. The expansion screw is located in the palate in close proximity to the

palatal contour. Buccal and lingual support wires also may be added for rigidity.

11. Double-hinged expander: A 2-hinged rapid maxillary expander in which the

expander is oriented perpendicular to the intermaxillary suture and is soldered to the

molar and premolar bands. Two anterior expansion arms (0.051 inch stainless steel

wires) extend bilaterally from the premolar bands toward central incisors.

12. Growth spurt: A rapid increase in height and weight, which typically occurs during

puberty.

5

ASSUMPTIONS

It was assumed that maxillary sutural separation will occur in the treated sample.

Furthermore, it was assumed that the maxilla will move forward and downward with

orthopedic force from protraction facemask therapy and that growth is constant

(i.e., there is no growth spurt). The final assumption was that the lateral cephalograms

for the treated and control groups were taken with the subjects in centric occlusion.

LIMITATIONS

1. Age differences amongst patients -- Growth spurts occurs at different times amongst

patients

2. Gender differences amongst patients

3. Ethnicity differences amongst patients

4. Health history differences amongst patients

5. Cooperation differences amongst patients / parents

DELIMITATIONS

1. Only two types of RPE appliances were used

a. Double-hinged expander

b. Hyrax expander

2. CVM was used to match the experimental and control groups

3. Class III patients before growth spurt were utilized in this study to minimize growth

differences among subjects.

6

CHAPTER II

LITERATURE REVIEW

The review of related literature on Class III malocclusion was divided into five

categories. These categories are listed below in order of presentation:

1. Prevalence of Class III malocclusion

2. Morphologic characteristics

3. Etiology

4. Diagnosis

5. Treatment of Class III malocclusion

PREVALENCE OF CLASS III MALOCCLUSION

The incidence of skeletal Class III malocclusion varies among different ethnic

groups. The prevalence among Caucasian population is approximately 3-5 percent.21-27

In the United States, the Class III malocclusion is a less commonly observed clinical

problem than Class II or Class I malocclusion and accounts for about 1% of the

population.7 In U.S. studies of African American population groups, the incidence of

Class III malocclusion was reported to be about 6.3 percent.28 Although few

epidemiologic studies are available for other racial groups, there is reportedly a higher

frequency of skeletal Class III malocclusion among the Oriental population.7 The

prevalence of Class III malocclusion in Japan has been reported to be 4-13%, and in

populations of Chinese descent it has been reported to be as high as 14.51% of the 834

children who were surveyed.8,9,29,30 Table 1 lists reported incidences of Class III

malocclusion.

7

Table 1. Reported Incidence of Class III Malocclusion.

Investigators Date Sample Incidence Ainsworth 27 1925 4,170 (2-15 years) 1.35% Huber & Reynolds 21 1946 500 (16-32 years) 12.2% Bjork31 1947 322 (boys 12 years) 2.8% Enrich et al. 32 1947 1,476 (12-14 years) 3% Humphreys et al. 22 1950 2,711 (2-5 years) 1.52% Massler & Frankel 23 1951 2,758 (14-18 years) 9.4% Hills et al. 24 1959 4,251 (6-8 years) 1% Altemus 33 1959 3,280 (12-16 years) 5% Allwright & Bundred30 1964 834 (6-11 years) 14.51% Horowitz & Doyle 34 1970 410 (9-14 years) 8.7% Garner & Butt 28 1985 445 (13-15 years) 6.3% MORPHOLOGIC CHARACTERISTICS OF CLASS III MALOCCLUSION

Patients with Class III malocclusion may present with various combinations of

abnormal dental and skeletal patterns. Dentally, patients with a Class III malocclusion

will tend to have the following characteristics: Angle Class III molars and canines,

retroclined mandibular incisors, proclined maxillary incisors, and edge-to-edge incisor

relationship or negative overjet. Patients with a skeletal Class III pattern, however,

typically present with a concave-appearing profile where the tip of the chin and the lower

lip will be in front of a vertical line drawn from nasion, perpendicular to the Frankfort

horizontal. Table 2 presents the various combinations of skeletal components of a Class

III malocclusion, as reported by Ellis and McNamara.6

8

Table 2. Prevalence of Maxillary and Mandibular Anterior-Posterior Deficiency

Group Maxilla Mandible % I Retrusive Protrusive 30.1 II Retrusive Neutral 19.5 III Neutral Protrusive 19.2 IV Protrusive Protrusive 14.9 V Retrusive Retrusive 7.9 VI Neutral Neutral 4.6 VII Neutral Retrusive 1.6 VIII Protrusive Neutral 1.6 IX Protrusive Retrusive 0.33

Based on the results found in Table 2, a retrusive maxilla and protrusive mandible

was the most prevalent skeletal combination in Class III malocclusion. A study

conducted by Guyer and colleagues5 reported similar results in that 25% of the 144

Michigan children, who were between the ages of 5 and 15 years and had a Class III

malocclusion with a retrusive maxilla and a protrusive mandible.

ETIOLOGY

The few human studies that focus on the role of genetics with regards to Class III

malocclusion support the belief that the growth and size of the mandible is predetermined

by hereditary.35,36 Other studies have found that Class III malocclusion also has an

environmental etiology. Rakosi and Schilli37 reported that individuals who mouth-

breathes or have mandibular postural habits may present with a Class III type of

malocclusion because the tongue tends to be flat and anteriorly displaced which then

results in the widening of the mandibular arch laterally and anteriorly. Discontinuation of

the habit allows for the malocclusion to self-correct. Rakosi and Schilli also noted that

interferences in occlusal function, such as reverse overjet, can alter the direction of

9

mandibular growth and the shape of the mandible. Early correction of a pseudo-Class III

malocclusion creates a more favorable development of the maxilla and mandible.37

SKELETAL CLASS III GROWTH.

Although functional disturbances play a small role in the number of Class III

malocclusions, it can definitely accentuate a Class III growth tendency. However, the

more severe Class III cases tend to be the result of genetics and can be worsened by

environmental factors.7 Therefore, to have a better understanding of the Class III skeletal

pattern it is important to review the growth of the cranial base, the nasomaxillary

complex, and the mandible.

Cranial Base Growth.

The cranium primarily grows by the following processes: (1) deposition on the

outer cortex; (2) resorption of the inner cortex; and (3) deposition in the spheno-occipital

synchondrosis. According to Enlow,38 the spheno-occipital synchondrosis is a major

growth center and enlarges by endochondral growth. Also, the spheno-occipital

synchondrosis has a pressure-adaptive growth mechanism that displaces bones as it

grows bi-directionally.

Many studies have focused on the relationship between the cranial base and facial

skeleton. Singh39 have found that the posterior cranial base length represented by Pc-Bo

(posterior clinoid process-Bolton point) was consistently and significantly shorter in pre-

pubertal Class III subjects. This provides support for the contention that the

development within the petro-occipital complex account for elongation of the posterior

cranial fossa. Thus, a developmental deficiency of the posterior cranial base could be

10

associated with the development of Class III malocclusion because of a prognathic

cranio-mandibular articulation.39

In addition, Hopkin40 and Jarvinen41 reported that Ar-SN (Articulare-SellaNasion)

angle was smaller in skeletal Class III patients as compared to skeletal Class II patients.

There have been many reports that an acute cranial base angle was correlated with

skeletal Class III malocclusion.40-43 In 2001, Hong44 demonstrated that subjects with

flexion of the cranial base tend to have a maxillary counterclockwise rotation in which

there was more vertical growth of the posterior maxilla, anterior rotation of the anterior

maxilla, and proclination of the upper incisors. According to Hong, the maxillary

rotational growth can affect the glenoid fossa and could consequently bring about

changes in the mandibular position.

The morphology of the cranial base is therefore an important factor in establishing

the antero-posterior relationship of the jaws. Class III individuals tend to have an

anterior cranial base that is wider and shorter, thereby establishing a foreshortened but

wider palate and maxillary arch. Also, the middle cranial fossa is aligned backward and

upward which then places the nasomaxillary complex in a more retrusive position and

creates the brachiocephalic facial form.

Nasomaxillary Complex.

Growth of the nasomaxillary area is a result of active growth at the maxillary

sutures and nose and passive, forward displacement of the maxilla created by growth in

the cranial base.7 As the maxilla moves downward and forward, the space at the sutures is

filled in by bone proliferation. Growth in the synchondroses decreases with the

completion of the neural growth around 7 years of age, and passive displacement of the

11

maxilla decreases as well. Active growth accounts for most of the forward movement of

the maxilla between ages 7 to 15 as seen in Table 3.

Table 3. Maxillary Length Changes. (From University of Michigan Center for Human Growth) AGE Total forward movement of the

maxilla (mm) (basion-ANS increment)

Forward displacement of the maxilla (mm) (basion-PNS increment)

Male Female Male Female 7 1.3 2.1 0.0 0.8 8 1.5 1.8 0.9 1.1 9 1.6 0.4 0.4 0.4 10 1.8 2.0 0.8 0.2 11 1.9 1.0 0.2 0.2 12 2.0 1.3 0.4 1.1 13 2.1 1.2 1.0 -0.1 14 1.1 1.5 0.3 0.1 15 1.2 1.1 0.4 0.8

Profitt7 and McNamara45 have reported normal growth of the maxilla is usually

1-2 mm per year, and there is a linear relationship with respect to the effective maxillary

length (Co-A point) as compared to the effective mandibular length (Co-Gn). Many

studies have reported that Class III skeletal malocclusions are due to a deficient maxillary

corpus length.31,46 Maxillary growth in the sagittal, vertical, and transverse dimensions

occurs at the fronto-maxillary, palato-maxillary, and midpalatal sutures. Any

developmental aberration will invariably affect the midfacial complex and result in

maxillary hypoplasia and midfacial retrusion. In turn, the dento-alveolar regions alone or

the entire midface can be affected. Singh found that the variability of the midfacial

complex in Class III malocclusions is due to developmental deficiency at the transverse

palatine suture and that acute angulation of the maxillary incisor acts as a compensatory

occlusal mechanism for the shorter maxilla relative to the longer mandible.39

12

Mandible

Mandibular growth involves bone deposition and resorption in a posterior and

superior direction. The condyle grows toward the glenoid fossa and displaces the entire

mandible in a forward and downward position.7 A hyperdivergent skeletal Class III

open-bite pattern exists when the following features are present: (1) a steeper mandibular

occlusal plane; (2) an increased gonial angle; (3) an increased mandibular plane angle;

(4) a more downward and backward location of the mandibular ramus; and (5) an

increased total anterior facial height and lower facial height.6 On the other hand, if the

ascending ramus is shorter and the gonial angle is more obtuse, then there exists a

hypodivergent or horizontal growth pattern of the jaw.47,48

Battagel48 found that the primary reason for a Class III incisor relationship was

because the lower jaw had an increase body length and because its articulation was more

ventrally located. Another common feature of Class III malocclusions is a more

anteriorly positioned condyle.49 Although an increased mandibular length is commonly

found in Class III malocclusions, the mandible’s position is responsible for most of its

prominence rather than its length.

DIAGNOSIS OF CLASS III MALOCCLUSION

Differential diagnosis of the skeletal Class III malocclusion is important in

attaining treatment success. However, the prognosis is obscure until growth is

completed. Furthermore, variations in magnitude and expression of the Class III

malocclusion can make diagnosing difficult. In order to differentiate the underlying

cause of a Class III malocclusion, a systematic approach should be employed. Several

authors have made the following recommendations in the assessment of Class III

13

patients.50-52 First and foremost, a thorough family history must be obtained because the

Class III malocclusion has a strong genetic component. Any facial (skeletal and dental)

characteristics that are shared among siblings, parents, and relatives, should be noted.

Next, perform a clinical exam and make note of the patient’s overall facial

proportions, chin position, midface profile, and assess the patient’s occlusion. An

examination of the occlusion should involve both a clinically judgment and a visual

analysis of high quality orthodontically trimmed study models. Components of the

occlusal exam should include: incisor relationship, overjet and overbite, maxillary and

mandibular incisor inclinations, buccal segment relationships, arch alignment (e.g.,

crowding, spacing, and rotations), crossbites, supernumerary/missing teeth, and dental

anomalies. Be sure to check for the presence of a functional shift by placing the patient

in centric relation (CR) and observing if the patient slides into centric occlusion (CO). If

the CO/CR discrepancy is due to an anterior functional shift, then the patient is

considered to have a pseudo-Class III malocclusion. In other words, this patient will

present with a Class I skeletal pattern, normal facial profile, and Class I molar relation in

centric relation, but in centric occlusion he/she will present as a Class III skeletal and

dental pattern. In this case, early treatment will benefit the patient and provide a

favorable maxillary and mandibular growth environment.

Following the clinical exam, one needs to quantitatively assess the severity of the

Class III malocclusion via cephalometric analysis (e.g., Wits appraisal, SNA, SNB, and

linear measurements of Condylion to A point, and Condylion to Gnathion). This will

help to determine the underlying cause of the jaw discrepancy. Finally, summarize the

diagnosis and include the nature of the malocclusion, the location of crowding or spacing,

14

and the severity of the skeletal pattern. A prioritization of the problem list will help in

strategically planning the sequence of treatment for the Class III malocclusion.

TREATMENT OF CLASS III MALOCCLUSION

Growing patient.

The goal of early orthodontic treatment is to provide a favorable environment for

dentofacial development and to prevent a more severe malocclusion in late

adolescensce.53 In 1981, Turpin54 presented guidelines for early treatment of Class III

malocclusions. He presented the positive and negative factors that may influence the

orthodontist’s decision of whether or not to start early treatment, and these factors are

listed in Table 4. Turpin also recommended that patients be made aware of the fact that

surgery is not to be ruled out, even though they may have a successful early treatment

phase.

Table 4. Positive and Negative Factors Influencing the Decision for Early Treatment.

Positive Factors Negative Factors Convergent facial type Divergent facial type Anterior-posterior functional shift No anterior-posterior shift Symmetrical condylar growth Asymmetrical growth Young, with remaining growth Growth complete Mild skeletal disharmony Severe skeletal disharmony Good cooperation expected Poor cooperation expected No familial prognathism Familial pattern established Good facial esthetics Poor facial esthetics Stages of Early Treatment for Class III Malocclsuion

Class III treatment in the growing patient can be categorized into the stages of

dental development (i.e., deciduous dentition, early mixed dentition, late mixed dentition,

and early permanent dentition) in order to help in deciding the appropriate treatment (e.g.,

15

non-extraction/camouflage treatment, an extraction/camouflage treatment, and functional

orthopedic appliances).

Deciduous Dentition. Because of the nature of the skeletal maturation at this

stage, anterior and posterior crossbites may be effectively treated in the primary

dentition.4 However, there has been little evidence to suggest that any orthodontic

intervention during the deciduous dentition stage can prevent or slow the development of

a Class III malocclusion. Thus, it may be better to wait until the patient is in the early

mixed dentition stage before considering orthodontic treatment to correct the

malocclusion, especially since ages six through nine years tend to provide the best patient

cooperation.

Early Mixed Dentition. Besides the advantage of patient cooperation,

orthodontic intervention during early mixed dentition can be beneficial for certain cases.

For example, early treatment should be provided for a patient who presents with a Class

III incisor relationship and a mandibular shift that is due to a premature contact.

Treatment of the functional shift may help prevent temporomandibular joint dysfunction

in adulthood.52

A shift caused by premature contacting deciduous canines can be treated by

enameloplasty of the cuspal interferences. If the shift is caused by premature contacting

of permanent incisors (i.e., a pseudo-Class III malocclusion), then a viable treatment

option would be the proclination of the incisors utilizing orthodontic brackets on the four

maxillary incisors and the maxillary first molars (2 x 4 ) or utilizing an upper removable

appliance incorporating either Z-springs or a screw-section if there is insufficient anterior

retention.52 Note that posterior bite planes may be incorporated into the treatment in

16

order to free the occlusion in cases where the overbite is deep. As with all treatment of

anterior crossbites, it is important to attain adequate overbite and to use retention in order

to successfully maintain the corrected incisor position.

Late Mixed Dentition. During late mixed dentition, it is important to provide

treatment for a patient who presents with a deep overbite (i.e., underbite) and a mild-to-

moderate skeletal Class III relationship where the maxillary and mandibular incisors are

proclined. However, because of the nature of the skeletal Class III malocclusion growth

modification is unpredictable especially where mandibular and/or vertical excess is

present. In the past, the Frankel III and chin-cup appliances were the treatment of choice

for the pubertal class III patient, but they lack long-term stability.55,56 Although

protraction facemask/RPE therapy is most effective during pre-pubertal growth, it is

currently considered to be the most appropriate treatment for patients with a retrusive

maxilla during the late mixed dentition stage.57 Moreover, rapid maxillary expansion

should be used in order to maximize the skeletal change when using protraction headgear.

Early Permanent Dentition. The goal of treatment in the early permanent

dentition stage is to produce a Class I incisor relationship and to attempt to compensate

for the underlying skeletal discrepancy. However, the clinician must be sure that skeletal

growth will not negate the treatment outcome, and the clinician should determine the

whether or not the patient has a severe skeletal discrepancy in which orthodontic

treatment would not be successful. Adolescents with a mild Class III skeletal

discrepancy may be treated effectively by proclining the maxillary incisors so as to create

positive overjet. For patients with a moderate skeletal discrepancy, proclination of the

17

upper incisors should be combined with retroclination of the lower incisors so as to

prevent an unstable and potentially traumatic occlusion.

If crowding is present, then extractions of the first premolars in mandibular arch

may be necessary. The maxillary arch crowding can sometimes be resolved by

proclining the incisors or via rapid palatal expansion. If crowding cannot be eliminated

in the maxillary arch, then extraction of the second premolars would be the treatment of

choice. 28

Non-growing patient

Finally, it should be noted that if pre-treatment dentoalveolar compensation

has already occurred, further treatment is often limited.

Once the patient has no remaining growth, treatment options are limited. The

treatment options that are available for Class III non-growing patients include non-

extraction/camouflage treatment, extraction/camouflage treatment, or surgery.

Sometimes a compromised treatment option may be employed because of the severity of

the skeletal discrepancy and if extraction or surgery is not an option. In these cases, an

alignment of the teeth may be achieved, but the occlusion will not be ideal. That is, a fair

amount of negative overjet may still persist due to skeletal discrepancies between the

maxilla and mandible.

Often, extractions are recommended to treat the malocclusion, mainly because it

will allow resolution of the crowding and because it will allow camouflaging of a

moderate skeletal discrepancy in which orthopedic correction is not possible. In addition,

extractions will allow the reduction in negative overjet which helps to camouflage the

skeletal discrepancy. Extraction patterns may vary depending on the amount of crowding

and/or the skeletal discrepancies in an adult patient.52

18

Orthognathic surgery is another option that is available for the non-growing Class

III patient. Although this treatment alternative will lead to the most ideal relationship of

the maxilla and mandible in severe malocclusions, it is also the most invasive and

expensive option. On the other hand, in cases of moderate or severe Class III

anteroposterior skeletal discrepancies where a vertical or transverse skeletal discrepancy

is present, surgery may be the only viable treatment option. Pre-surgical orthodontic

treatment necessitates both alignment and decompensation of the axial inclination of the

incisors. According to McIntyre52 the maxillary incisors are retroclined and the

mandibular incisors are proclined to approximately 109° and 90°, respectively to the

maxillary and mandibular planes. A short period of orthodontic treatment (about 6

months) is often required following surgery to finish and detail the occlusion.

Methods of Early Treatment of Class III Malocclusion

As previously discussed, there are more treatment options available for correcting

the Class III malocclusion in a growing patient as opposed to non-growing patients. The

following discussion explains some of the available methods of early treatment for Class

III malocclusions.

2x4 Appliance. In 2004, Hagg, Tse, Bendeus, and Rabi, conducted a study in

which 25 patients (mean age of 10.2 years) with a pseudo-Class III malocclusion were

treated with 2 x 4 appliance.58 These patients were observed for five years post-

treatment. Of the 25 patients, only 5 patients had subsequent full comprehensive

orthodontic treatment to correct crowding. The researchers found that young patients

treated early with 2 x 4 appliance were able to attain long-term stability overjet

correction.

19

Frankel III (FR-3). Only a few articles published on the Frankel III appliance

(FR-3) provided scientific basis on which treatment results were claimed. The Frankel III

appliance is designed to counteract the muscle forces acting on the maxillary complex.59

The upper portion of the appliance has vestibular shields in the depths of the sulcus that

placed away from the alveolar buccal plates of the maxilla in order to allow the maxilla to

develop anteriorly. In contrast, the vestibular shield is fitted closely to the mandibular

alveolar process so as to hold or redirect growth posteriorly. Robertson56 monitored 12

Class III patients (mean age was 9.4 years) who were treated with FR-3 for 2 years.

These patients experienced overjet correction primarily through dentoalveolar changes in

(i.e., crown tipping).

A study by Loh and Kerr 60 reviewed the lateral cephalometric radiographs of 20

patients treated with FR-3. There was not a control group, and the mean treatment time

was 3.1 years +/- 1.9 years. The results of the study indicated that the FR-3 appears to

have proclined the upper incisors and retroclined the lower incisors. Also, the mandible

repositioned in downward and backward direction which in turn increased the facial

height. There were minimal skeletal changes with respect to the maxilla. The authors

concluded that the best indication for using a FR-3 would be in a young, early mixed

dentition patient with Class III malocclusion and an overbite of 4-5 mm.

In a study by Ulgen and Firatli 61, 20 patients with functional Class III

malocclusions were treated with FR-3. These patients showed a significant increase in

the ANB angle as compared to the 20 untreated subjects in the control group who also

had functional Class III malocclusion. The patients in both groups were able to

reposition their mandible backward into an anterior edge-to-edge position. The

20

significant increase in the treatment group’s ANB angle was mostly due to a decrease in

SNB as the mandible rotated downward and backward. No significant changes in SNA

were reported. The authors claim that the treatment period in this study was shorter

compared to others and that there was poor patient cooperation.

In conclusion, the use of the FR-3 may not be the ideal choice for treatment of

patients who present with maxillary anteroposterior deficiency as the primary etiology.

However, this appliance may have some clinical application, particularly in patients who

present with any existing hyperactivity in the muscles associated with the maxilla.59

Petit62, McNamara63 and Brudon45 recommended the use of FR-3 for retention after

protraction headgear therapy.

Chin Cup Therapy. The use of appliances resembling chin cups to help reduce a

prognathic mandible was reported as early as the 1800’s. Graber 64 attempted to explain

that the failure associated with the early trials of chin-cup therapy was because of the lack

of complete understanding of facial growth which lead to an unsuitable amount of force

to be used or to the use of the chin cup after the skeletal growth has been completed. In

1977, Graber treated 30 skeletal Class III Caucasian children, averaging six years of age,

with chin cup therapy for a period of three years. He compared this treated group to an

untreated Class III control group and found that the treated group had a posterior rotation

of the mandible, a decrease gonial angle, a restriction in vertical condylar growth, and a

“clockwise rotation” of the maxilla. Mitani and Sakamoto65 reported similar results to

the Graber’s study. The authors followed three Japanese females treated with the chin

cup and found that the mandibular growth was altered to a downward and backward

direction for all three patients.

21

In 1986, Mitani and Fukazawa66 evaluated growth changes in the mandible when

orthopedic force is applied during the pubertal period in 26 Japanese females. The

patients were examined in the pre-peak, peak, and post-peak pubertal growth periods.

Also, the treatment group was compared to a control group of Class I subjects around the

same age. There findings of this study were interesting, especially the fact that subjects

all exhibited some incremental growth of the mandible during use of the chin cup in all

three stages, especially during the peak stage. Thus, the authors concluded that

orthopedic force does not alter the innate growth of the mandible.

A study by Ritucii and Nanda67 in 1986 focused on the effects of using the chin

cup on the maxilla and the cranial base. The treated and control sample sizes were small

in that there were only 10 treated Class III patients and 7 untreated Class I control. The

authors reported significant inhibition of anterior and posterior vertical maxillary growth

and a clockwise rotation of the maxilla. They explained that the maxillary clockwise

rotation occurred because the inhibition of posterior vertical development was greater

than the anterior.

In 1990, Sugawara et al.55 found similar results to the aforementioned study in

which they concluded chin cup has no effect on the anteroposterior growth of the

midface. The skeletal profile showed great improvement during the initial stages of chin

cup therapy, but the patients later had a mandibular displacement in a forward and

downward direction before growth was completed. Therefore, chin cup therapy does not

necessarily guarantee correction of skeletal profile after completion of growth.

In 1993, Allen and colleagues68 found that the overjet correction that resulted

from the use of chin cup is attributed to proclination of upper incisors, retroclination of

22

lower incisors, and downward movement of the mandible. A significant change of the

ANB angle was not noted. Consequently, the authors questioned whether the chin cup

brings about a change in the anteroposterior jaw relationship.

In summary, among the published studies chin cup therapy have shown varying

results in the attempts to restrict mandibular growth. According to Sugawara et al.55

clinicians should not overestimate the effects of a chin cap appliance to correct skeletal

facial profiles. For patients who present with skeletal Class III malocclusion due

primarily to maxillary anteroposterior deficiency, the chin cup therapy would not address

the underlying problem.55,67

Protraction Facemask Therapy. In the past few decades, protraction facemask

therapy increased in popularity largely due to the awareness of the role that maxillary

deficiency has in contributing to the skeletal Class III malocclusion5,6,40. One of the first

people to have mentioned the clinical effects of maxillary protraction was Dr. Albin

Oppenhein in 1944, when he presented three cases in which the Class III patients were

treated using a chin cup with spurs to which a maxillary lingual arch was attached via

elastics.69

In the 1960s, Delaire introduced a modification to the chin cup which included a

forehead support and an interlabial bow with spurs for elastic attachment.70 Around the

same time that Delaire introduced the facial mask, Haas reported the use of maxillary

expansion alone can move the maxilla forward and downward, resulting in a mandibular

downward and backward rotation.15 Protraction facemask therapy used in conjunction

with rapid maxillary expansion appliance has been shown to be successful in correcting

skeletal Class III malocclusions that are due to deficient maxillary development and /or

23

mandibular prognathism.9-12,30,71,72 In the 1970s, several primate studies showed

dramatic skeletal changes and helped to explain the anatomical effects of continuous

forces on maxillary protraction.73-76

Animal Studies. In 1973, Dellinger76 conducted a study on anterior maxillary

displacement using two Macaca speciosa monkeys. He used rapid maxillary expansion

and connected it to a spring device that delivered an anterior force of six pounds on the

maxilla. A significant amount (2.0 mm and 2.8 mm) of maxilla anterior displacement

was noted in seven days.

In 1977, Kambara74 studied the possible effects of extra-oral forward force on the

growth of the dentofacial group of five monkeys; however, no maxillary expansion

device was employed. An intermittent force of 300 grams was applied to the maxilla

bilaterally for 15 hours per day. The results were significant changes in the circum-

maxillary sutures with a small degree of counterclockwise rotation of the maxilla.

Histologic preparations showed that the significant changes may have resulted from an

opening of the suture, stretching of sutural connective tissue fibers, and new bone

deposition along the stretched fibers. Sutural width was maintained through homeostasis.

Kambara concluded that further studies are needed to evaluate post-treatment relapse.

In a 1978 study on six Macaca mulatta monkeys with three controls, Nanda75

noted that the extra-oral forces helped to displace the maxilla anteriorly. An anterior

force of 500 grams was delivered for 81-95 days to a bar that extended anteriorly from a

splint fastened to the maxillary arch. Furthermore, Nanda found that maxillary

movement was related to the direction of force. With the exception of one treated

monkey, the maxilla’s angle of rotation directly correlated to line-of-force angle. For

24

instance, as the line-of-force became more parallel to the occlusal plane, less maxillary

rotation occurred in which a relatively more horizontal movement was noted.

However, the results from the 1979 study conducted by Jackson et al. 73 contradict

Nanda’s findings. They found that a steeper line-of-force to the occlusal plane produced

a greater amount of maxillary rotation and vertical displacement. Jackson, Kokich and

Shapiro performed the study on four Macaca nemestrina monkeys with no control group,

and they documented that when the anterior extra-oral traction was applied parallel to the

occlusal plane the maxillary complex had significant anterior positioning with a slight

amount of counter-clockwise rotation. In addition, the authors noted a substantial degree

of relapse due to reorientation of the maxillary complex after active treatment was

completed. Therefore, a period of stabilization following the application of force to the

maxilla may be necessary to minimize the amount of post-treatment relapse.

Human Studies. Protraction headgear effects in humans have been reported by

many investigators 10-12,62,70,71,77-79 However, the person mainly responsible for reviving

the interest in the protraction headgear technique was Delaire.70 Later, Petit 62 modified

the Delaire’s basic concepts by increasing the amount of time that the facemask is worn

and the amount of force generated by the appliance, thus attaining dramatic results within

a shorter time period.

Since 1970 when Haas15 showed downward and forward maxillary displacement

with the use of palatal expansion, many clinical studies have noted that the use of a

palatal expander in conjunction with protraction headgear enhanced maxillary

protraction. 10-12,71,77 Palatal expansion helps to disarticulate the maxilla and initiates

cellular response in the suture, allowing a more positive reaction to protraction forces.15

25

In 1980, Nanda77 demonstrated the use of modified protraction headgear in

patients prior to their adolescent growth spurt. Rapid palatal expansion and/or the use of

the chin cup was often combined with the use of the protraction headgear, and the author

reported favorable results after 4 to 8 months of protraction headgear treatment. The

maxilla and dentition displaced anteriorly about 1-3 mm and 1-4mm, respectively.

In 1987, Wisth and colleagues78 evaluated lateral cephalograms of 22 children,

between 5-10 years of age, who presented with a Class III malocclusion and were treated

with the protraction facemask for 3-12 months. These patients placed on an observation

period of 6-48 months. The researchers compared the before, during, and after treatment

results to that of a control group of individuals with normal occlusion and found that 18

of the 22 children had a significant decrease in mandibular prognathism with overjet

correction. The changes observed during retention were found to be comparable to the

control groups. The authors concluded that maxillary protraction had a normalizing

effect not only on the negative overjet but also on the general face morphology.

McNamara10 and Turley11 reported similar findings with the use of the maxillary

protraction appliance. Treatment results included forward and downward movement of

the maxilla along with anterior and downward maxillary tooth movement. They also

found that the mandible moved downward and rotated backwards, thus increasing lower

facial height and creating an overall improvement of soft tissue contour.

In a 1992 preliminary study by Ngan and co-workers 12, ten Class III patients who

treated with protraction headgear and fixed palatal expansion appliance were found to

have had significant overjet and molar corrections after six months of treatment. The

correction of the Class III malocclusion was primarily due to the maxilla’s forward and

26

downward movement and the mandible’s downward and backward rotation. From this

study, the authors concluded that a long-term follow-up study is needed to assess the

stability of this treatment modality.

A year later, Takada and colleagues79 conducted a study in which they treated

Japanese female children using a modified maxillary protraction headgear and chin cup.

The treatment group was divided into three categories according to their age: pre-

pubertal (7-10 years), mid-pubertal (10-12 years), and late pubertal (12-15 years) and the

average treatment time was 1.1, 1.0, and 1.4 years, respectively. There was a significant

increase in maxillary length for the pre-pubertal and mid-pubertal groups, but results

were not as significant in the late pubertal group.

Ngan and colleagues71 found similar results in their 1996 study in which 30

Chinese Class III patients who were treated with protraction headgear and rapid palatal

expansion. The patients showed a change in overjet which went from a negative value to

a positive value of approximately 6.2 mm after six months of treatment. The results are

partly due to the anterior movement of the maxilla and the posterior rotation of the

mandible. There was also a one degree counter-clockwise rotation of the maxilla that

occurred as a result of the 30 degree downward elastic pull from the occlusal plane.

In 1998, Nartallo-Turley80 examined 21 females between the ages of 3.9 to 10.8

years of age who were treated with palatal expansion and facemask therapy for an

average of 11 months and found that the facemask therapy produced a statistically

significant anterior movement of the maxilla (SNA angle increased by 2.4 degree and

ANB angle increased by 3.7 degrees). The mandible had a significant downward

movement when measured at Menton, and the occlusal plane analysis showed that the

27

maxilla contributed more to the correction than did the mandible. There were also dental

changes that contributed to the molar and overjet correction in that the upper molars and

incisors moved forward by 1.7mm and 1.8mm, respectively. Overall, the palatal

expansion with facemask therapy produced both skeletal and dental changes that

contributed to the Class III correction.

A 2002 study conducted by Keles et al.81 examined the effect of varying the force

and direction of the maxillary protraction. A total of 20 patients with Class III

malocclusion due to a retruded maxilla were randomly divided into two groups. Both

groups had a rapid palatal expander that was activated twice a day for 10 days and then

protraction facemask therapy was initiated. Group 1 had a unilateral 500 gram force that

was applied forward and downward in a direction 30 degrees angle relative to the

occlusal plane; whereas, group 2 had the same amount of force applied extraorally but at

20 mm above the maxillary occlusal plane. Both groups had effective maxillary

protraction; however, the maxilla advanced forward with a counter-clockwise rotation in

group 1 and had only an anterior translation without rotation in group 2. The dental

effects in both groups were also different in that the maxillary incisors were slightly

proclined in group 1 but were retroclined and extruded in group 2. The authors concluded

that counter-clockwise rotation can be prevented if the force application is near the center

of resistance of the maxilla. This would be especially useful for patients who present as

Class III malocclusion along with an anterior open bite.

Miniplates for Anchorage During Maxillary Protraction. Most orthopedic

appliances use the teeth for anchorage which yields unwanted dental side effects such as

dental anchorage loss or maxillary counter-clockwise rotation. In the past, it was shown

28

that forces can be applied to ankylosed teeth or implants to help prevent dental anchorage

loss during maxillary protraction.5,82 The more recent studies on the subject of

protraction facemask therapy involve the use of osseo-integrated implants/screws and

mini-plates for anchorage during maxillary expansion and protraction.

The use of osseo-integrated implants as skeletal anchorage has been successful in

several studies. In 1998, Smalley et al.83 were able to gain significant disarticulation of

the circum-maxillary sutures and remodeling of the bony surfaces in monkeys via the use

of osseo-integrated implants as anchorage for protraction of the maxillofacial complex.

Movassaghi et al.16 also did an animal study but used skeletally immature rabbits. They

were able to distract the nasal bones of these rabbits from the frontal cranial segment and

induced bone formation across the frontonasal suture. In 2000, Singer et al.84 placed

titanium implants in the zygomatic buttress area in a 12-year and 1-month-old female

patient with a Class III malocclusion secondary to repair of a unilateral cleft lip and

palate defect. The implants were allowed to osseo-integrate for 6 months then customized

abutments that projected into the buccal sulcus were placed. Elastic force of 400 g per

side was applied from a facemask to the implants at 30 degrees to the occlusal plane for

14 hours per day for 8 months (ages 12 years and 10 months to 13 years and 6 months).

The results were the downward and forward maxilla movement of 4 mm along with an

anterior maxillary rotation which in turn rotated the mandible open. In addition, there was

an increase in nasal prominence as the maxilla advanced which contributed to the

increase in facial convexity. The researchers were able to avoid the unwanted dental

changes frequently seen in standard facemask therapy, and the anterior maxillary

displacement was stable for 1 year post-treatment.

29

In the late 1990s and early 2000, titanium mini-plates became popular primarily

as an alternative to orthognathic surgery for treating openbites, especially because the

miniplates assisted in intruding molars.83,85,86 In 2005, Beyza et al. 87 presented a case

report in which titanium mini-plates were used as skeletal anchorage for orthopedic

protraction in an 11-year-old girl who presented with severe maxillary hypoplasia and

hypodontia. The mini-plates were placed on the lateral nasal wall of the maxilla to serve

as anchorage for facemask protraction, and intraosseous titanium screws were placed on

the palatal bone near the alveolar crest in order to provide anchorage for palatal

expansion. After 7mm of expansion, protraction facemask therapy was initiated. The

patient experienced 8mm of anterior maxillary movement with an increase in SNA of 7o

and a decrease in SNB of 3 degrees. The mandible did rotate posteriorly and the palatal

plane angle rotated 2 o counterclockwise. Beyza et al. stated that by using the mini-

plates, they were able to take advantage of the sutural growth potential because the

orthopedic forces were directed to the sutural sites. Furthermore, the researchers

attributed their success to the location of the mini-plate anchorage because the lateral

nasal wall is anterior to all of the sutures joining the maxilla to the cranial base and

because its location was anterior to the center of resistance of the maxilla.

Effective Maxillary Protraction. As previously discussed, effective maxillary

protraction is dependent upon many variables, especially overcoming resistance of the

circum-maxillary sutures. Maxillary expansion aids in the disarticulation of the maxilla.

Recall that Haas reported the use of maxillary expansion alone can move the maxilla

forward and downward, resulting in a mandibular downward and backward rotation.15

Furthermore, protraction facemask therapy used in conjunction with rapid maxillary

30

expansion appliance has been shown to be successful in correcting skeletal Class III

malocclusions related to deficient maxillary development and /or mandibular

prognathism.9-12,30,71,72 However, most protraction techniques use the teeth for anchorage

and result in unwanted dental side effects. Moreover, traditional protraction facemask

therapy has only produced about 1.5 – 3mm of protraction per year.17,18,88

Despite the other studies results, Liou and Tsai1 have been able to achieve an

average of 5.8mm of maxillary advancement (horizontal movement at A point) using

only toothborne devices. They attribute their success partly to the use of a new double-

hinged rapid maxillary expander which is designed to expand and rotate each half of the

maxilla outward, allowing greater anterior displacement with a reduced risk of bone

resorption in the tuberosity area.1-3 In his 2005 report, Liou and Tsai 1 described the use

of the double-hinged expander along with an Alternate Rapid Maxillary Expansion and

Constrict (Alt-RAMEC) protocol in which the maxilla is expanded 1mm per day for one

week and then constricted 1mm per day for the following week. This protocol lasted for

a period of seven to nine weeks. Afterwards, instead of using a protraction facemask, a

pair of fixed, toothborne 0.036” TMA helical springs along with mandibular anchorage

from a 0.036” TMA lingual holding arch is used to protract the maxilla. Although

protraction facemask can be used, the intra-oral protraction springs eliminate the reliance

on patient cooperation. Liou and Tsai concluded that the most important element to their

success is the Alt-RAMEC protocol because it helped to loosen the maxillary suture and

therefore allowed for the maxilla to be orthopedically protracted without significant

unwanted dental side-effects.

31

In March 2009, Wang, Chang, and Liou89 reported the results of their animal

study in which they attempted to quantitatively analyze the opening of the circum-

maxillary suture after the Alt-RAMEC protocol. Twelve cats were randomly grouped

into two groups of six in which group 1 was expanded for one week and group two had

five weeks of alternating expansion and constriction. The double-hinged expander was

used in both groups. The animals were sacrificed at the end of the experiment and the

nasomaxillary complexes were preserved in 10% formalin in order to examine the

circum-maxillary suture opening. The researchers conclude that Alt-RAMEC opens the

sutures both sagitally and coronally more than the conventional rapid maxillary

expansion technique. Furthermore, the sutures that ran sagittally were opened

significantly more than the sutures that ran coronally, whether or not they were connected

to the maxilla directly.

Given the success that Liou et al.1-3,89 have been able to achieve with the double-

hinged expander, this study will compare the quantitative difference, if any, between the

conventional protraction technique that uses the traditional Hyrax expander and the new

protraction protocol with the double-hinged expander as advocated by Liou. The skeletal

and dental changes with maxillary expansion and protraction will be measured. Finally,

the differences between the two techniques will be evaluated on lateral cephalometric

radiographs.

32

CHAPTER III

MATERIALS AND METHODS

SAMPLE DESCRIPTION

All patients included in this study were between the ages of 6 to 12 years old and

have a Class III malocclusion with no craniofacial anomaly. The stage of dental

development varied from early to late mixed dentition, and all subjects had an overjet

ranging from -5.6 mm to + 3.9 mm prior to the start of the treatment. The treated sample

had lateral cephalograms taken before treatment and after 6 months of protraction

facemask therapy in order to evaluate treatment changes. Table 5 illustrates the symbols

used to represent the different time intervals at which lateral cephalograms were taken.

Note that the mean treatment time was 9 months + 3 months. A Frankel III appliance

was given to patients following treatment to help maintain Class III correction. Table 6

reports the chronological age distribution of both treated groups and the control group.

TABLE 5. Symbols for the different time intervals.

Symbol Definition

t1

Control subject’s radiograph taken at an age corresponding to double-hinged expansion patient’s before treatment age

t2

Control subject’s radiograph taken 6 months the first radiograph (t1)

T1

Treated subject’s radiograph taken before treatment

T2

Treated subject’s radiograph taken 6 months after the start of protraction facemask therapy

33

Table 6. Chronologic Age Distribution of Treatment and Control Samples

AGE

Double-Hinged

Expander Group

Hyrax

Expander Group Control Group

(Years) Female Male Mean Female Male Mean Female Male Mean

T1 or t1 8.6 + 0.9

8.3 + 1.0

8.5 + 1.2

8.6

+ 0.7

8.7

+ 1.5

8.6

+ 1.2 8.5

+ 1.0 8.4

+ 1.3 8.4

+ 1.1

T2 or t2 9.6 + 1.5

9.5 + 1.2

9.5 + 1.1

9.6

+ 0.5

9.3

+ 1.1

9.4

+ 1.2 9.5

+ 1.6 9.4

+ 1.4 9.4

+ 1.5

The Double-hinged expander group consisted of seven Caucasians, one Chinese,

and one African-American, subjects. Of these subjects, there were four females and five

males who presented with Class III skeletal malocclusion and were treated at the West

Virginia University School of Dentistry Department of Orthodontics. At the start of

treatment, the average age of the female patients were 8.6 + 0.9 years of age, and the

average age for the male patients was 8.3 + 0.9 years of age. A lateral cephalogram was

taken prior to treatment. Then, these patients were treated with maxillary expansion

using a Double-hinged expander along with the alternating expansion and constriction

(Alt-RAMEC) protocol as described by Liou et al.1-3 Following maxillary expansion,

protraction facemask therapy was prescribed for approximately 9 months for 10-12 hours

of wearing time per night.

The Hyrax expander group consisted of lateral cephalometric radiographs of nine

Chinese subjects who were closely matched in age, sex, and pretreatment skeletal

morphology to the Double-hinged expansion treatment group. These patients were treated

with maxillary expansion and protraction facemasks in the Department of Children’s

Dentistry and Orthodontics, Faculty of dentistry, University of Hong Kong. After 6

34

months of protraction facemask therapy, a new lateral cephalometric radiograph was

taken on the Hyrax expander subjects to assess treatment effects.

The control group consisted of nine Chinese subjects who were closely matched

in age, sex, and pretreatment skeletal morphology to the Double-hinged expansion

treatment group. Serial lateral cephalometric radiographs were taken on untreated

patients with a Class III malocclusion in order to monitor their growth. Note that the

control group subjects were eventually treated with rapid palatal expansion and

protraction facemask therapy. However, the lateral cephalometric radiographs selected

for this study were both taken before treatment and are six months apart. The

radiographs are denoted as (t1) and (t2).

For this study, the cervical vertebra maturation level was reviewed in all treated

and control group subjects in order to assess the subjects’ skeletal age and to account for

any differences in treatment outcome that may be due to the pubertal growth spurt. Table

7 illustrates the CVM levels of all patients in this study.

Table 7. CVM of Treatment and Control Samples

CVM (Stage 1-5)

Double-Hinged Expander Group

Hyrax

Expander Group Control Group

Sig.

Time Mean SD Mean SD Mean SD

T1 or t1 1.22 0.44

1.33

0.50 1.44 0.53

N.S.

T2 or t2 1.56 0.73

1.67

0.50 2.00 0.71

N.S. NS = not significantly different * = significantly different at p < 0.05.

35

The cervical maturation assessment used in this study was based on the new

Cervical Vertebral Maturation (CVM) method developed and employed by Baccetti,

Franchi, and McNamara.90 It should be noted that at the start of treatment, all subjects

were at the CVM stage 1-2, and at the end of treatment all subjects were at CVM stage 2-

3. Therefore, all subjects have not undergone a pubertal growth spurt during treatment.

Table 6 displays the mean CVM stage in the treated groups and control group at times T1

and T2.

RESEARCH DESIGN

Appliance Design and Expansion Protocol Hyrax Rapid Palatal Expander.

The Hyrax rapid palatal expander is an orthopedic appliance that widens the

maxillary halves (Figure 1). In fabricating the Hyrax rapid palatal expander bands were

fitted on the posterior teeth. In the primary dentition, the bands were fitted on the

maxillary deciduous first and second molars. In the mixed dentition, bands were fitted on

the second deciduous molars and on the permanent first molars. After the bands were

fitted, a maxillary alginate impression was made. The bands were soldered to heavy

wires (0.045 inch) which were connected to a jackscrew that is centered along the

midline of the maxillary palate. Bilaterally, 0.045 inch wire was soldered to the buccal

aspects of the molar bands, and extended anteriorly to the canine area. This buccal wire

has a curve at the canine area so that elastics can be used to connect the appliance to a

protraction facemask. The patient activated the appliance two times per day (once in the

morning and once at night with each turn being 0.25mm) for 1 week. Patients with a

narrow maxilla activated the expansion screw for 2 weeks.

36

Figure 1. Hyrax expander Figure 2. Double-hinged expander with protraction hooks with protraction hooks. Double-Hinged Expander

The double-hinged expander (Figure 2) is an orthopedic appliance that was

designed for greater anterior displacement of maxilla. The double-hinged expander

consists of 2 rotational hinges in the posterior, a jackscrew in the center, and 0.051 inch

wires attached to the expander.3 When activated, the double-hinged expander rotates each

half of the maxilla outward through the two hinges. This allows for expansion that

entails forward rotation of maxilla with a decreased likelihood of bone resorption behind

the maxillary tuberosities.1-3 Similar to the fabrication of the Hyrax expander, the teeth

that were used as anchorage for the double-hinged expander were the posterior teeth.

That is, in the primary dentition the bands were fitted on the maxillary deciduous first and

second molars; whereas, in the mixed dentition bands were fitted on the second

deciduous molars and on the permanent first molars. After the bands were fitted, a

compound impression of the banded teeth and a maxillary alginate impression were

made. The impression with the fitted bands was poured in silky rock stone and sent to a

lab for the fabrication of the double-hinged expander.

37

The expander is soldered to the molar bands and positioned perpendicular to the

intermaxillary suture. Bilaterally, 0.045 inch wire was soldered to the buccal aspects of

the molar bands, and extended anteriorly to the canine area. This buccal wire has a curve

at the canine area so that elastics can be used to connect the appliance to a protraction

facemask. In some cases, a lingual wire (0.045 inch wire) was soldered to the molar

bands and was extended to the cingulum of the maxillary incisors to increase anchorage

control, if needed. The bands are sandblasted prior to cementation. On the day of

cementation, the double-hinged expander is activated according to the Alt-RAMEC as

listed below. 1,2

Alternate Rapid Maxillary Expansions and Constrictions (Alt-RAMEC).

Alt-RAMEC is a protocol in which the maxilla is rapidly expanded and

constricted on an alternating weekly basis 1,2 According to Liou et al, it takes seven to

nine weeks to loosen the maxilla. For this study, a seven-week protocol was used. The

weekly protocol is as follows: (1) 7mm of expansion, (2) 7mm of constriction, (3) 7 mm

of expansion, (4) 7 mm of constriction, (5) 7 mm of expansion, (6) 7mm of constriction,

and (7) 7 mm of expansion. The maxilla is expanded or constricted 1 mm per day (two

turns in the morning and two turns at night). Patients were recalled after the first week,

the second week, the fifth week, and finally the seventh week. The maxilla must be

loosened before proceeding for maxillary protraction. The maxilla could be clinically

examined for mobility by holding patient’s head with one hand and rocking the expander

with maxilla up and down with another hand. At the seventh week, protraction facemask

therapy was begun, and the patient was recalled six weeks after the start of protraction

facemask therapy.

38

Protraction Facemask.

The Petit-Delaire protraction facemask is a one-piece construction with adjustable

forehead padding, adjustable chin cup, and an adjustable anterior bar (Figure 3). The

adjustable components of the protraction facemask allows for proper positioning of the

chin cup for comfort upon opening and closing and of the proper position of the anterior

bar to which elastics were attached to both left and right sides. To avoid an opening of

the bite as the maxilla is protracted, the elastics were attached near the maxillary canines

with a downward and forward pull of 30 degrees to the occlusal plane. Maxillary

protraction generally requires 300 to 600 grams of force per side, depending on the

patient. In this study, a Correx Haag-Streit Bern gauge was used to measure the elastic

force on the Double-hinged expander patients in order to ensure that approximately 380

grams of force was generated on each side. Patients were instructed to wear the

protraction facemask for 10-12 hours a day, which includes nighttime wear. The Hyrax

expander patients were instructed to wear the protraction face for 12 hours per day. Like

the Double-hinged expander group, the elastics were gauged to produce 380 grams of

force per side.

Figure 3. Protraction Facemask

39

METHODOLOGY

Lateral cephalometric radiographs were taken at the following time periods:

before treatment (T1) and 6 months of treatment with protraction (T2). All radiographs

were taken in the same cephalostat with the teeth in habitual occlusion, the lips in repose.

Tracing of the lateral cephalograms were performed on 0.003 inch matte acetate tracing

film with a 0.75 mm mechanical #2 lead pencil. The researcher traced all radiographs

with the use of a lighted 12 ¼” x 11 ½” x 2 ¼” cephalometric viewbox. The midpoint

bisecting the two images was used where cephalometric landmarks had right and left

images.

Measurements of each variable were performed twice with the use of a

cephalometric protractor or a Fowler-Sylvac Ulta-Cal Mark III electronic caliper as

shown in Figure 4. The caliper was calibrated to zero before each measurement, and the

average of the two measurements was recorded. Sagittal and vertical measurements were

recorded to the nearest 0.01mm, and angular measurements were reported to the nearest

0.1 degree.

Figure 4. Acetate Tracing paper, lighted viewbox, cephalometric protractor, electronic caliper, mechanical pencil, and lead.

40

Reliability of Cephalometric Measurements

This part of the study analyzed the error in locating, superimposing, and

measuring the changes of the different landmarks by one examiner (intra-examiner error).

Lateral cephalograms at t1 and t2 of nine subjects in the control group and lateral

cephalograms at T1 and T2 of the nine subjects in each treatment group were used for

this part of the analysis. Each series of cephalograms of the total twenty-seven subjects

were recorded independently at two separate occasions, two weeks apart. While tracing

the radiographs, the examiner was aware of when the cephalograms were taken (e.g., at

T1 or T2). Calculations were made to determine the differences between the independent

repeated measurements of each cephalometric variable at T1 and T2 (or t1 and t2).

Any measurement with more than 1.00 mm or 1.0 degree difference between the first and

second measurement was eliminated from the database, and the cephalometric variable

was then measured again twice to get more accurate and precise measurements. Also, the

superimposition error was calculated to show the treatment changes of the twenty-seven

subjects. Other data recorded include the arithmetic mean, standard deviation (S.D.), and

minimum and maximum of each cephalometric variables. These calculations are listed in

Appendix A through H.

41

Cephalometric Landmarks and Reference Planes

The cephalometric landmarks described by Bjork91 and Pancherz 92 were used in

this study and are defined in Table 8 and Figure 5. The reference lines used are defined

in Table 9 and Figure 6. Sagittal, vertical, and angular measurements were performed on

each lateral cephalogram tracing.

Figure 5. The skeletal and dental landmarks (see Table 7 for definitions).

42

Table 8. The seventeen skeletal and dental landmarks.

Name Symbol Definition Sella S The center of the sella turcica Nasion N The most anterior point of the naso-frontal suture Anterior nasal spine ANS The apex of the spina nasalis anterior Posterior nasal spine PNS The most posterior point on contour of the palate in the

midsagittal plane Subspinale A pt. The deepest point in the concavity of the anterior

maxilla between the ANS and the alveolar crest Supramentale B pt. The deepest point in the concavity of the anterior

mandible between the alveolar crest and pogonion Pogonion Pg The most prominent point on the chin Menton Me The deepest point of the mandibular symphysis Gonion Go The lowest point of the bony contour of the angle of the

mandible Maxillary incisor apex

Isa The root apex of the most prominent maxillary central incisor

Maxillary incisor edge

Is The incisal point of the most prominent maxillary central incisor

Mandibular incisor apex

Iia The root apex of the most prominent mandibular central incisor

Mandibular incisor edge

Ii The incisal point of the most prominent mandibular central incisor

Molar superius mesial cusp

Msc The mesio-buccal cusp tip of the maxillary second primary molar or first permanent molar

Molar superius Ms The mesial contact point of the maxillary primary second molar or permanent first molar

Molar inferius Mic The mesial-buccal cusp tip of the mandibular primary second molar or permanent first molar

Molar inferius Mi The mesial contact point of the mandibular primary second molar or permanent first molar

Table 9. Definition of the reference lines.

Name Symbol Definition Sella-Nasion plane SNL Reference line joining Nasion and Sella Maxillary plane NL Reference line joining anterior nasal spine and

posterior nasal spine Occlusal plane OLs Reference line joining maxillary incisal edge and the

molar superious mesial cusp tip Mandibular plane ML Reference line joining menton and gonion Occlusal plane perpendicular

OLp Reference line produced by dropping a perpendicular line from sella to the occlusal plane

43

Figure 6. The Reference Grid (OLs and OLp) and Measuring Points Used in the Sagittal Cephalometric Analysis.

Measuring Procedure for Sagittal Changes.

The occlusal plane (OLs) and the occlusal plane perpendicular (OLp) from the

tracing of T1, the before treatment lateral cephalogram, formed the reference grid. This

reference grid was used for all the sagittal skeletal and dental measurements which

analyzed the distance between the OLp and the cephalometric landmarks as shown in

Figure 6. The grid was then transferred to T2, the 6-month post-protraction facemask

therapy lateral cephalogram. Note that the T1 tracing was superimposed on the T2 tracing

using the sella-nasion line (NSL) and along the anterior cranial base structure. The

distance between OLp and the cephalometric landmarks on the T2 tracing were

measured. The reference grid was only used for sagittal measurements on the

superimpositions. The nine sagittal variables are listed in Table 10.

44

Table 10. The Sagittal Measurements of Variables (1-9).

Variable (mm) Definition Skeletal measuring points: 1. OLp – A pt. Position of maxillary base 2. OLp – B pt. Position of mandibular base 3. OLp – Pg Position of mandibular chin Dental measuring points: 4. Is/OLp Position of maxillary central incisor 5. Ii/OLp Position of mandibular central incisor 6. Overjet Is/OLp minus Ii/OLp 7. Ms/OLp Position of maxillary second primary or first permanent molar 8. Mi/OLp Position of mandibular second primary or first permanent molar 9. Molar Rel Molar relationship: Ms/OLp minus Mi/OLp

Measuring Procedure for Vertical Changes.

Figure 7 illustrates the reference line and planes used in vertical measurements,

and the seven vertical measuring points are listed in Table 11.

Figure 7. The Reference Lines and Measuring Points Used in the Vertical Cephalometric Analysis.

45

Table 11. The vertical measurements of variables (10-16).

Variable (mm) Definition

Skeletal measuring points: 10. N-A pt. Maxillary vertical positioning 11. ANS-Me Lower facial height Dental measuring points: 12. Is-NL Position of maxillary central incisor (measured Is NL) 13. Ii-ML Position of mandibular central incisor (measured Ii ML) 14. Overbite Distance from Ii OLs 15. Msc – NL Position of maxillary primary second or permanent first molar

(Msc NL) 16. Mic – ML Position of mandibular primary second or permanent first

molar (Mic ML) Measuring Procedure for Angular Changes.

The reference lines and measuring points used for angular measurements are

illustrated in Figure 8. The eight variables are listed in Table 12.

Figure 8. The Reference Lines and Measuring Points Used for the Angular Cephalometric Analysis

46

Table 12. The angular measurements of variables (17-24).

Variable (o)

Definition

Skeletal measuring points: 17. SNA Maxillary base relative to SNL 18. SNB Mandibular base relative to SNL 19. ANB SNA minus SNB 20. SNL – ML Mandibular plane angle 21. SNL – OLs Occlusal plane angle 22. SNL – NL Palatal plane angle Dental measuring points: 23. Is/SNL Maxillary central incisor angle 24. Ii/ ML Mandibular central incisor angle Evaluation of Overjet and Molar Relationship Correction

The amount of dental changes that occurred within the maxilla and mandible was

calculated in order to determine the amount of skeletal and dental contribution to the

overjet and molar relationship correction. The calculation method is shown below in

Table 13.

Table 13. Calculation of overjet and molar relationship changes.

Overjet Molar relationship

Skeletal contribution Skeletal contribution:

1. OLp – A pt. 1. OLp – A pt.

2. OLp – Pg 2. OLp – Pg

Dental contribution Dental contribution

3. Is/OLp minus OLp – A pt. 3. Ms/OLp minus OLp – A pt.

4. Ii/OLp minus OLp – Pg 4. Mi/OLp minus OLp – Pg

Overjet correction Molar relationship correction

Sum of 1, 2, 3, and 4 Sum of 1, 2, 3, and 4

47

STATISTICAL TREATMENT

Arithmetic mean (mean) and standard deviation (SD) was calculated for each

cephalometric variable. The JMP statistical software on a MacIntosh computer was used

to analyze the data. To determine the reliability of cephalometric measurements, the

Intraclass Correlation Coefficient of Reliability (I.C.C.R.) was used, in which MSA is the

mean square among the variables, MSE is the mean square between the variables, and k

is the number of repeated measures:

R = (MSA – MSE) / MSA + [(k-1) MSE]

The R value is a number between zero and one, and an R value greater than 0.90

indicates high reliability.

The 3x2 ANOVA was used to assess the statistical significance with regards to

the differences in dentofacial morphology of the subjects in the three groups (e.g.,

Double-hinged group, Hyrax group, and Control group) at two different time periods

(e.g., T1 and T2). The Tukey-Kramer Multiple Comparison Test was done to find the

statistical significance when comparing two groups at a time (e.g., Control group vs.

Hyrax expander group; Hyrax expander group vs. Double-hinged expander group; and

Control group vs. Double-hinged expander group). A level of significance used include:

p< 0.05, p < 0.01, and p < 0.001. However, p > 0.05 was designated as not significant

(N.S.)

48

EQUIPMENT AND MATERIALS

Hyrax 12 mm expander

(Summit Orthodontic Services, Inc. in Munroe Falls, OH 44262)

Double-hinged 12 mm expander

(Best Medical & Dental International, Inc. in Kaohsiung, Taiwan)

Petit-Delaire Protraction face-mask

(Ormco Corporation in Glendora, CA 91740)

Fowler –Sylvac Ultra-Cal Mark III electronic caliper

(Salem Tools in Salem, Virginia)

Cephalometric acetate tracing paper

(3M Unitek in Monrovia, California)

Cephalometric protractor

(3M Unitek in Monrovia, California)

Bic mechanical pencil

(BIC Corporation in Shelton, CT 06484-6299 USA)

12 ¼” x 11 ½” x 2 ¼” cephalometric tracing box and viewer.

(Henry Schein, 5 Harbor Park Drive, Port Washington, NY 11050)

JMP statistical software for MacIntosh computer

49

CHAPTER IV

RESULTS AND DISCUSSION

RESULTS

This section presents the results and discussion of the study which investigated

the quantitative difference, if any, between the two techniques of maxillary expansion

and protraction. The traditional technique of using a Hyrax expander to expand the

maxilla once prior to using the protraction facemask was compared to that of another

technique which employs a double-hinged expansion appliance to expand and contract

the maxilla multiple times prior to maxillary protraction. The results of the double-

hinged expander group and the Hyrax expander group were compared to a matched

control group.

Changes in the measurement points were assessed. The arithmetic mean, standard

deviations, minimum, and maximum were calculated separately for both treated groups

and the control group. The maxillary expansion and protraction facemask effects in the

two treated groups were compared to one another as well as to that of the control group in

order to find any statistical significant differences. The statistical results from this study

are discussed in the following order:

1. Reliability of cephalometric measurements

a. Error of sagittal measurements

b. Error of vertical measurements

c. Error of angular measurements

d. Error of superimposition

50

2. Statistical significance within the Double-hinged Expander group (DH) between

T1 and T2

3. Statistical significance within the Hyrax Expander group (H) between T1 and

T2

4. Statistical significance within the Control group (C) between t1 and t2

5. Statistical significance among the three groups (DH, H, and C) for the time

periods T1 and T2 in the treated groups and t1 and t2 in the control group.


The Intraclass Correlation Coefficient of Reliability (I.C.C.R.) for sagittal,

vertical, angular, and superimposition measurements are listed in TABLE 14. The errors

made by one examiner (i.e., the intra-examiner error) when locating the different

landmarks, superimposing the tracings, and measuring the changes of the landmarks, are

illustrated in Appendix A through D.

51

Table 14. Intraclass Correlation Coefficient of Reliability for Sagittal, Vertical, Angular Measurements, and Superimpositions

Variable

Name T1 T2 T2-T1

Mean

Difference Reliability Mean

Difference Reliability Mean

Difference Reliability

Skeletal OLp – A pt. 0.39 0.98979 -0.07 0.99649 -0.46 0.75415 OLp – B pt. -0.15 0.99929 -0.19 0.99856 -0.04 0.83303 OLp – Pg -0.09 0.99981 -0.37 0.99650 -0.28 0.83192 Dental Is / OLp 0.10 0.99874 -0.11 0.99943 -0.21 0.98587 Ii/ OLp -0.01 0.99859 -0.08 0.99896 -0.07 0.98526 Overjet 0.12 0.98737 -0.03 0.99490 -0.15 0.95158 Ms/OLp -0.09 0.99982 -0.24 0.99861 -0.15 0.98521 Mi/OLp 0.05 0.99983 -0.08 0.99945 -0.13 0.73011 Molar Relationship

-0.14 0.99819 -0.16 0.93338 -0.02 0.96216

Skeletal N - A pt 0.05 0.99941 -0.10 0.99874 -0.05 0.97030 ANS – Me -0.32 0.99920 -0.19 0.99754 0.13 0.98788 Dental Is – NL 0.12 0.99560 -0.13 0.99563 -0.25 0.95383 Ii – ML -0.16 0.99933 0.16 0.99780 0.24 0.94953 Overbite -0.42 0.99489 -0.13 0.99960 0.21 0.99568 Msc – NL 0.35 0.98518 0.12 0.99346 -0.24 0.89454 Mic – ML -0.01 0.99934 0.15 0.99832 0.16 0.99221 Skeletal SNA -0.3 0.99575 0.3 0.99183 0.6 0.95158 SNB 0.2 0.99527 -0.1 0.99036 -0.3 0.71981 ANB -0.5 0.99552 0.4 0.99754 0.9 0.96112 SNL – ML -0.1 0.99136 -0.4 0.99991 -0.4 0.99405 SNL – OLs 0.0 0.99732 0.1 0.99854 -0.6 0.98337 SNL – NL 0.2 0.99553 -0.4 0.88566 0.3 0.97119 Dental Is / SNL 0.1 0.99964 -0.4 0.99993 -0.5 0.99357 Ii / ML 1.9 0.99394 0.4 0.89261 -1.5 0.92210

SAG

ITT

AL

(mm

) V

ER

TIC

AL

(mm

) A

NG

UL

AR

()

52

Error in Sagittal Measurements. The I.C.C.R. for all sagittal measurements and

time periods were found to be greater than 0.93, which indicates that the measurements

are reliable. The greatest error measurements was found to be 0.39 mm for the maxillary

base position (OLp – A pt.) measured at time T1. Appendix E lists the mean, standard

deviation, minimum, and maximum of the sagittal measurements.

Error in Vertical Measurements. The I.C.C.R. for all the vertical measurements

and time periods were found to be greater than 0.98, which indicates that the

measurements are reliable. The greatest error measurement was found to be 0.35 mm for

the variable which measures the maxillary primary second or permanent first molar

relative to the palatal plane (Msc - NL) at time T1. The mean, standard deviation,

minimum, and maximum of the vertical measurements are listed in Appendix F.

Error in Angular Measurements. The I.C.C.R. for all except two of the angular

measurements and time periods were found to be greater than 0.88, which indicates that

the measurements are reliable. The greatest mean error measurement was found to be

1.9o for the maxillary central incisor angle (Ii/ML) measured at time T1. The mean,

standard deviation, minimum, and maximum of the angular measurements are listed in

Appendix G.

Error in Superimpostion. The I.C.C.R. for all superimposition measurements was

found to be greater than 0.81, which is considered to be reliable. The greatest mean error

measurement was 0.90 mm for the ANB variable at T2-T1, but it had a reliability

coefficient of 0.96. The mean, standard deviation, minimum, and maximum of the

superimposition measurements are listed in Appendix H.

53

Statistical Significance Within the Treated Group

Cephalometric measurements at T1 and T2 with regards to the sagittal, vertical,

and angular variables are listed in Appendices E through G.

Comparison of T1and T2 for the Double-Hinged Expansion Group. Statistically

significant differences for sagittal, vertical, and angular changes for the Double-hinged

expander group are listed in Tables 15, 16, and 17, respectively. The arithmetic mean,

standard deviations, minimum, and maximum for the sagittal, vertical, and angular

changes are also shown in Tables 15, 16, and 17.

Table 15. Sagittal measurements at T1 and T2 in the Double-hinged Expander Group

Variables (mm) T1 T2 Matched Pair t-test*

Sagittal Min Max Mean Min Max Mean p-value Sig. Skeletal 1. OLp – A pt.

69.76 83.22 77.88 72.11 83.82 79.70 0.0003 ***

2. OLp – B pt.

79.97 92.10 85.12 79.54 91.28 83.75 0.0043 N.S.

3. OLp – Pg

81.59 95.00 87.19 79.44 95.57 86.13 0.1316 N.S.

Dental 4. Is/OLp

75.56 90.86 83.89 80.74 94.99 87.19 0.0014 **

5. Ii/ OLp

79.77 91.25 84.64 78.96 90.27 82.77 0.0338 *

6. Overjet -4.22 3.75 -0.76 0.51 6.96 4.43 0.0001 ***

7. Ms/OLp

44.78 57.90 52.97 46.06 61.95 54.99 0.0008 ***

8. Mi/OLp

49.35 64.83 56.86 49.03 63.21 55.52 0.0245 *

9. Molar Rel. -7.97 0.31 -3.89 -3.00 4.41 -0.53 0.0003 ***

NS = not significantly different * = significantly different at p < 0.05. ** = shows pairs of means that are significantly at p < 0.01 *** = shows pairs of means that are significantly at p < 0.001

54

With regards to the sagittal measurements, significant differences were found in

all except two cephalometric variables tested as illustrated in Table 15. Skeletally, the

position of the maxillary base (OLp – A pt.) increased from T1 to T2. Dentally,

maxillary incisor (Is/OLp) had significant forward movement and mandibular incisor

(Ii/OLp) had significant backward movement. Overjet improved significantly from -0.72

mm to 4.51 mm, a 4.82 mm correction following maxillary expansion and protraction,

while molar relationship had a significant correction from a Class III relationship of -4.01

mm to a minimal Class III relationship of -0.66 mm following treatment.

Table 16 shows the vertical variables measured at times T1 and T2 for the

Double-hinged expander group.

Table 16. Vertical measurements at T1and T2 in the Double-hinged Expander Group.


Vertical Min Max Mean Min Max Mean p-value Sig. Skeletal 10. N-A pt. 50.07 63.18 55.57 49.18 64.03 55.96 0.2695 N.S.

11. ANS – Me 61.51 75.88 67.34 64.04 77.49 68.62 0.1362 N.S.

Dental 12. Is – NL 25.64 32.25 27.91 24.95 30.63 27.42 0.8699 N.S.

13. Ii – ML 36.13 42.50 39.00 37.76 43.95 40.74 0.0013 **

14. Overbite -0.88 5.16 2.15 -2.07 5.46 2.02 0.8171 N.S.

15. Msc – NL 14.98 23.98 18.96 16.37 24.28 19.00 0.9816 N.S.

16. Mic – ML 25.00 33.72 29.47 25.08 32.10 30.08 0.1769 N.S.


55

Of the seven vertical variables, the one measuring the mandibular central incisor

position (Ii ⊥ ML) was the only variable that had a significant change, starting at 39.00

mm and becoming 40.74 mm.

Table 17 shows the angular measurements for the Double-hinged expander group

at times T1 and T2.

Table 17. Angular measurements at T1 and T2 in Double-hinged Expander Group

Variables (o) T1 T2 Matched Pair t-test*

Angular Min Max Mean Min Max Mean p-value Sig. Skeletal 17. SNA 72.0 82.5 79.3 74.5 88.6 80.8 0.0629 N.S.

18. SNB 72.5 81.5 79.2 71.5 81.5 78.1 0.0071 **

19. ANB -3.5 4.0 0.2 -1.0 -7.6 2.7 0.0038 **

20. SNL - ML 30.0 38.5 20.9 28.0 39.5 20.7 0.0071 N.S.

21. SNL - OLs 15.0 26.5 20.9 14.0 26.5 20.7 0.5862 N.S.

22. SNL - NL 2.0 11.5 5.8 1.5 10.0 5.8 1.0000 N.S.

Dental 23. Is/ SNL 83.0 116.0 98.6 90.0 117.0 104.1 0.0172 *

24. Ii /ML 72.0 94.0 84.9 76.0 91.0 83.6 0.5166 N.S.


Significant differences were found with the variables: SNB, ANB, and maxillary

incisor angle (Is / SNL). The SNB angle decreased from 79.17 o to 78.06 o, whereas ANB

56

significantly increased from 0.17o to 2.73o following treatment. The maxillary incisor

angle also increased after treatment, going from 98.61 o to 104.11 o.

Comparison of T1 and T2 for Hyrax Expansion Group. Statistical analyses to

determine significant differences among the various time periods of the Hyrax expansion

group with regards to the sagittal, vertical, and angular changes are listed in Tables 18,

19, and 20, respectively. Arithmetic mean, standard deviations, minimum, and maximum

for the sagittal, vertical, and angular changes are shown in Appendices E-G.

Table 18. Sagittal measurements at T1 and T2 in Hyrax expander treatment group


Sagittal Min Max Mean Min Max Mean p-value Sig. Skeletal 1. OLp – A pt.

62.66 70.45 67.65 66.03 73.59 70.49 0.0007 ***

2. OLp – B pt.

71.49 85.75 76.72 69.71 82.28 75.55 0.2570 N.S.

3. OLp – Pg

71.82 87.75 78.29 70.98 83.83 77.30 0.4480 N.S.

Dental 4. Is/OLp

71.30 77.73 74.97 74.07 84.61 79.49 0.0021 **

5. Ii/ OLp

74.40 80.59 77.74 70.04 80.96 75.98 0.1209 N.S.

6. Overjet -4.06 -1.63 -2.77 1.24 7.18 3.51 0.0014 **

7. Ms/OLp

40.67 59.53 48.52 46.33 65.57 52.41 0.0012 **

8. Mi/OLp

45.76 65.19 51.65 45.24 65.16 52.41 0.1234 N.S.

9. Molar Rel. -6.90 -1.00 -3.12 -2.77 1.09 0.01 0.0081 **


57

Table 18 lists the significant differences that were found in the sagittal variables.

Significant changes skeletally in the position of maxillary base (OLp – A pt.). Dentally,

there were significant sagittal changes in the position of the maxillary central incisor and

overjet. Also, there were significant changes in the position of the maxillary second

primary or first permanent molar position and thus in the molar relationship. The overjet

started out at a mean of -2.69 mm and corrected to a mean of +1.99 mm. Molar

relationship was changed significantly from a Class III molar relationship, -2.66 mm, to a

near Class I relationship of -0.37 mm, for total 2.29 mm correction following six months

of treatment with protraction facemask.

Table 19. Vertical measurements at T1 and T2 in Hyrax Expander Group


Vertical Min Max Mean Min Max Mean p-value Sig. Skeletal 10. N-A pt. 49.03 57.41 53.48 46.34 58.20 53.72 0.7913 N.S.

11. ANS – Me 57.44 62.68 60.50 59.74 69.07 63.57 0.0037 **

Dental 12. Is – NL 21.63 27.87 25.78 23.07 27.80 26.24 0.0036 **

13. Ii – ML 35.02 39.87 37.51 36.88 41.53 39.07 0.0527 *

14. Overbite -0.78 9.46 3.41 0.36 4.06 2.22 0.2547 N.S.

15. Msc – NL 15.47 21.09 18.48 17.88 21.84 19.77 0.0051 **

16. Mic – ML 25.45 31.13 28.04 26.33 32.18 29.42 0.0085 **


58

Significant differences were found in five of the seven vertical variables, as

illustrated in Table 19. No significant changes were observed with the maxillary vertical

position (N-A pt.) and overbite. Skeletally, there were significant changes in lower facial

height (ANS - Me). Dentally, there was not significant decrease in overbite, but there was

a significant vertical change in position of the maxillary and mandibular central incisor as

well as the maxillary and mandibular primary second or permanent first molar.

Statistically significant differences were found in only two of the eight angular

variables, as illustrated in Table 20.

Table 20. Angular measurements at T1 and T2 in Hyrax Expander Group

Variables (o) T1 T2 Matched Pair t-test*

Angular Min Max Mean Min Max Mean p-value Sig. Skeletal 17. SNA 76.0 83.0 78.7 77.5 86.0 80.8 0.0001 ***

18. SNB 77.0 85.0 79.4 76.0 82.0 78.4 0.0633 N.S.

19. ANB -5.5 3.0 -0.9 1.0 4.5 2.7 0.0011 **

20. SNL - ML 32.5 40.0 23.1 34.5 2.0 21.6 0.1185 N.S.

21. SNL - OLs 15.5 29.0 23.1 15.5 25.5 21.6 0.1185 N.S.

22. SNL - NL 2.0 12.5 8.1 2.5 11.0 7.6 0.3336 N.S.

Dental 23. Is/ SNL 91.5 122.0 104.5 98.5 117.0 109.2 0.0653 N.S.

24. Ii /ML 73.0 106.5 91.3 76.5 105.5 88.1 0.1963 N.S.


59

Skeletally, SNA and ANB angles had a significant increase of over 2o following

treatment with maxillary expansion and protraction facemask. However, the SNB angle,

palatal plane angle, occlusal plane angle, and mandibular plane angle did not decrease

significantly following treatment. Otherwise, there were no significant changes dentally.

Statistical Significance Within the Control Group

The lateral cephalometric radiographs of the control group were measured and

compared for the two different time intervals. The arithmetic mean, standard deviation

(SD), minimum, and maximum of all variables are listed in Appendices E-G.

Comparison of t1 and t2. Statistical analyses for the control group’s sagittal,

vertical, and angular changes are shown in Tables 21, 22, and 23, respectively.

Statistically significant differences between times t1 and t2 were found in five of the nine

sagittal variables listed in Table 21. Skeletally, there were significant changes in the

position of the mandibular base (OLp – B pt) and the position of the mandibular chin

(OLp – Pg). Dentally, there was no significant change in the overjet, the molar

relationship, and the maxillary incisor sagittal position (Is/OLp). The mandibular incisor

edge, however, did have a significant forward movement relative to the occlusal plane

perpendicular reference line (Ii/OLp). Other significant changes included forward

movement of the maxillary molar (Ms/OLp) and the mandibular molar (Mi/OLp), all of

which may be attributed to growth.

60

Table 21. Sagittal Measurements at t1 and t2 for the Control Group

Variables (mm) t1 t2 Matched Pair t-test*

Sagittal Min Max Mean Min Max Mean p-value Sig. Skeletal 1. OLp – A pt. 65.62 74.89 69.37 66.84 75.31 69.93 0.0699 N.S.

2. OLp – B pt. 70.76 88.05 76.73 72.92 89.40 78.22 0.0291 *

3. OLp – Pg 71.43 90.00 78.35 73.28 91.51 80.31 0.0307 *

Dental 4. Is/OLp 71.63 83.72 75.12 71.51 85.47 76.34 0.0688 N.S.

5. Ii/ OLp 73.83 86.13 77.77 74.18 87.80 79.51 0.0271 *

6. Overjet -4.56 -1.87 -2.67 -4.62 -2.34 -3.17 0.1195 N.S.

7. Ms/OLp 42.63 56.57 47.87 44.88 58.09 49.38 0.0128 *

8. Mi/OLp 43.90 61.99 50.92 47.48 63.81 52.96 0.0151 *

9. Molar Rel. -7.45 -0.04 -3.05 -8.48 -1.21 -3.58 0.1584 N.S.


The control group subjects experienced significant increases in all seven vertical

variables. Table 22 lists the vertical changes that had occurred in each variable. No

significant changes in the angular variables for the control group subjects, as illustrated in

Table 23.

61

Table 22. Vertical measurements at t1 and t2 in Control Group

Variables (mm)

t1 t2 Matched Pair t-test*

Vertical Min Max Mean Min Max Mean p-value

Sig.

Skeletal 10. N-A pt. 49.11 55.22 52.67 50.83 57.38 54.42 0.0027 **

11. ANS – Me 55.27 70.03 61.25 58.49 70.22 63.23 0.0097 **

Dental 12. Is – NL 19.57 30.18 23.88 20.92 31.56 26.07 0.0031 **

13. Ii – ML 37.33 43.16 40.37 37.96 44.94 41.88 0.0002 ***

14. Overbite 1.79 7.02 3.46 3.72 7.33 5.25 0.0008 ***

15. Msc – NL 13.24 21.75 17.24 15.66 21.54 18.84 0.0038 **

16. Mic – ML 26.51 31.93 29.60 27.71 33.92 30.59 0.0081 **


62

Table 23. Angular measurements at t1 and t2 in Control Group

Variables (o) t1 t2 Matched Pair t-test*

Angular Min Max Mean Min Max Mean p-value Sig. Skeletal 17. SNA 75 83.5 80.3 74.5 84.5 79.7 0.3549 N.S.

18. SNB 75.5 85 79.6 76.5 86 79.9 0.5675 N.S.

19. ANB -3 2.5 -0.1 -3 4.5 0 0.8131 N.S.

20. SNL - ML 32 41.5 36.2 30.5 41 36.2 0.2389 N.S.

21. SNL - OLs 17 28 21.6 15 29.5 22.7 0.2389 N.S.

22. SNL - NL 4 12 8.4 4 12 8.2 0.8183 N.S.

Dental 23. Is/ SNL 95.5 107 101 90 113 101.2 0.9377 N.S.

24. Ii /ML 81.5 96 89.2 81 100 88.9 0.9185 N.S.

NS = not significantly different Comparison of Treated and Control Groups

The effects with maxillary expansion and protraction facemask in the Double-

hinged expansion group and the Hyrax expansion group were compared to one another

other as well as to the control group. The comparison of the 24 variables at each time

interval is illustrated in Tables 24. The ANOVA showed significant differences among

the three groups for the following 12 variables: OLp- A pt., OLp-B pt., OLp-Pg, Ii/OLp,

Overjet, Mi/OLp, Molar Relationship, N-A pt., Is-NL, Overbite, SNA, and ANB.

Afterwards, the Tukey-Kramer procedure was used to analyze the difference among the

paired groups. The results of the statistical analyses can also be found in Table 24.

63

Table 24. Comparison of the Mean Difference Among all Groups

Variable Name Double-hinged (DH)

Hyrax (H)

Control (C)

ANOVA Tukey-Kramer (pairs showing

significant differences) Mean SD Mean SD Mean SD p-value Sig Skeletal

OLp - A pt

1.78 0.86 2.57 1.43 0.63 0.90 0.0038 ** H, C OLp - B pt

-1.23 1.74 -0.60 1.47 1.53 1.73 0.0043 ** H, C DH, C

OLp – Pg

-1.05 1.87 -0.49 1.84 1.95 2.24 0.0089 ** H,C DH, C

Dental Is / OLp 3.28 2.07 3.18 2.15 1.32 1.88 0.0913 N.S. Ii/ OLp -1.95 2.28 -1.50 2.59 1.83 2.04 0.0036 ** H, C

DH,C Overjet 5.22 2.08 4.68 2.93 -0.51 0.88 0.0001 *** H,C

DH, C Ms/OLp 2.10 1.22 3.40 2.08 1.57 1.48 0.0696 N.S. Mi/OLp -1.25 1.35 1.10 1.92 2.04 1.99 0.0019 ** H, DH

DH, C Molar Relationship

3.35 1.64 2.30 1.97 -0.47 0.91 0.0001 *** H,C DH, C

Skeletal N - A pt 0.54 1.37 0.10 1.11 1.63 1.14 0.0369 * H, C ANS – Me 1.34 2.43 3.13 2.33 1.86 1.65 0.2157 N.S. Dental Is – NL 0.06 1.12 0.86 0.63 2.16 1.56 0.0031 ** DH, C Ii – ML 1.89 1.17 2.62 3.46 1.50 0.70 0.5403 N.S. Overbite -0.13 1.65 -1.25 3.05 1.88 1.09 0.0138 * H, C Msc – NL -0.02 2.10 1.21 0.94 1.50 1.12 0.0899 N.S. Mic – ML 0.68 1.37 1.38 1.20 1.02 0.88 0.4545 N.S. Skeletal

SNA 1.4 2.0 2.1 0.7 -0.6 1.9 0.0054 ** H, C DH, C

SNB -1.1 0.9 -1.0 1.4 0.3 1.7 0.0630 N.S. ANB 2.6 1.9 3.6 2.2 0.1 1.4 0.0016 ** H, C

DH, C SNL – ML 1.6 0.5 1.7 0.5 -0.2 0.5 0.0297 * H,C SNL – OLs -0.2 1.2 -1.5 2.6 1.1 2.6 0.0637 N.S SNL – NL 0.0 2.7 -0.5 1.5 -0.2 2.8 0.9055 N.S.

Dental Is / SNL 5.5 5.5 4.7 6.6 0.2 6.2 0.1588 N.S. Ii / ML -1.3 5.9 -3.2 6.8 -0.2 6.3 0.6053 N.S.

DH = Double-hinged H = Hyrax C = Control NS = not significantly different * = significantly different at p < 0.05. ** = shows pairs of means that are significantly at p < 0.01 *** = shows pairs of means that are significantly at p < 0.001

SAG

ITT

AL

(mm

) V

ER

TIC

AL

(mm

) A

NG

UL

AR

(o )

64

To summarize Table 24, significant skeletal and dental sagittal differences were

found between the Hyrax expansion group (H) and the control (C) group for the

following variables: OLp-A pt., OLp-B pt., OLp-Pg, Ii/OLp, Overjet, Molar

Relationship, N-A pt., Overbite, SNA, and ANB. The Double-hinged expansion group

(DH) and the control group had statistically significant differences for the following

variables: OLp-B pt., OLp-Pg, Ii/OLp, Overjet, Mi/OLp, Molar Relationship, Is-NL,

SNA, and ANB. The Double-hinged expander group and the Hyrax group only had one

statistically significant difference, which was related to the variable Mi/OLp.

The majority of the significant differences that were found between the treated

groups and the control group were in the sagittal variables. Skeletally, both the Double-

hinged and Hyrax expander groups display significant difference from the control group

with regards to the position of the mandibular base (OLp-B pt.) and chin (OLp – Pg) only

because the control group subjects experienced a significant change in the two

aforementioned measurement variables. Although both treated groups had significant

changes to the maxillary base position (OLp – A pt.), only the Hyrax group had a

significant difference as compared to the control group.

Dentally, the Double-hinged expander group showed significant changes in all

measurement variables but only had significant differences in four of the six

measurement variables when compared to the control group. Although both treated

groups had significant changes to the maxillary central incisor position (Is/OLp), it was

not significantly different from the control group. The position of the mandibular incisor

(Ii/OLp), however, was significantly different in the treated groups versus the control

65

group. The Double-hinged expansion group had a -1.95 mm change and the Hyrax group

had a -1.50 mm change, compared to the control group’s +1.83mm change.

Furthermore, the position of the mandibular molar (Mi/OLp) in the Double-

hinged expander group significantly differs that of the Hyrax expander group as well as

that of the control group. The Double-hinged expander group and the control group

experienced a significant change in the mandibular molar position (Mi/OLp). Double-

hinged expander patients had -1.25mm of mean difference from time T1 to T2; whereas,

the control group subjects had a +2.04 mm mean difference from time t1 to t2. Note that

all three groups (control and treated) had significant changes in the maxillary molar

position (Ms/OLp) but there were no statistically significant differences among the three

groups.

The use of maxillary expansion and protraction facemask affect both the skeletal

and dental changes; therefore, they must be taken into consideration when referring to

overjet and molar relationship corrections. In other words, the downward and backward

movement of the mandible will in turn change the position of the measuring points

associated with the sagittal variables OLp-Pg, Ii/OLp, and Mi/OLp, which will become

more negative. As a result, the overjet and molar relationship will appear to have

improved closer to a Class I relationship because the negative values will be added to the

overjet and molar relationship. On the other hand, positive values of the aforementioned

variables will be subtracted to determine the overjet and molar relationship. Method for

calculating the overjet and molar relationship correction in the treated group was

mentioned in Table 13.

66

Diagrams of sagittal changes of the two treatment groups that occurred between

times T1 and T2 as compared to that of the control group between times t1 and t2 are

shown in Figures 9 and 10, respectively. In addition, calculations accounting for the

skeletal and dental contributions to overjet and molar relationship are listed in Figures 9

and 10. Besides the skeletal and dental changes, one must take into consideration the

contributions that growth may have in order to truly appreciate the treatment effects.

Figures 9 and 10 also show the treatment effect (i.e., changes from the treatment minus

changes due to growth).

67

Figure 9. Total Observation (Double Hinged): Sagittal Changes

Figure 10. Total Observation (Hyrax): Sagittal Changes

68

Both treated groups had significant changes to overjet and in turn were

significantly different when compared to the control group’s minimal change in overjet.

However, upon closer examination once growth is accounted for, it is evident that the

Double-hinged expander a greater change (+5.74 mm) to overjet as opposed to the Hyrax

expansion group (+5.19 mm).

In addition, both treated groups had significant changes to molar relationship and

were significantly different from the control group. Interestingly, the treatment effect

(after subtracting growth) with regards to the molar relationship correction in the double-

hinged expander subjects (+3.82 mm) was less than that of the Hyrax expander subjects

(+5.95 mm) in molar relationship.

Diagrams of vertical and angular changes of the two treatment groups that

occurred between times T1 and T2 as compared to that of the control group between

times t1 and t2 are shown in Figures 11 and 12, respectively. Growth is also taken into

account in order to get the actual treatment effects, and this is illustrated in Figures 11

and 12.

69

Figure 11. Total Observation (Double Hinged): Vertical and Angular Changes

Figure 12. Total Observation (Hyrax): Vertical and Angular Changes

70

Of the seven vertical variables, only three of the variables had significant

differences amongst the control and treated groups. The control group had significant

changes in all seven vertical variables but was only significantly different from the Hyrax

group with respect to the N-A pt and the overbite. The control group’s N-A pt. increased

significantly by +1.63 mm, and the control group’s underbite increased by +1.88 mm. In

contrast, the Hyrax group had significant changes in all measurement variables except the

N-A pt. and overbite. The maxillary incisor vertical position relative to palatal plane (Is -

NL) in the Double-hinged expander group measured only 0.06 mm more at time T2 than

T1 and was significantly different from that of the control group, which had a significant

change of +2.16 mm to its vertical maxillary position.

Statistically significant differences between the three groups were found in two of

the eight angular variables when reviewing the changes at time T2 in the treated groups

and time t2 control group, respectively. The ANB angle showed a significant increase in

the treated groups (+2.57o for the Double-hinged group and +3.61o for the Hyrax group)

and was significantly different from the control group. The Double-hinged expander

group experienced a significant decrease in the angular measurement of SNB; whereas,

the Hyrax expander group experienced a significant increase in the angular measurement

of SNA. Furthermore, the Double-hinged expander group showed a significant increase

in the maxillary central incisor angle (Is/ SNL), but when compared to the Hyrax

expander group and the control group, there were no statistically significant differences

among the three groups.

71

DISCUSSION


The method of cephalometric analysis used in this study was based Pancherz’s

method of cephalometric analysis 92. The error of most variables was within an

acceptable limit for the treatment changes, as illustrated in Appendices A-D, and was

therefore considered reliable.

It has been shown that identification error for different cephalometric landmarks

can vary widely. However, Tng performed a study on human skulls in which he took a

series of cephalograms with reference steel ball markers glued on the skulls to represent

the “true” skeletal and dental landmarks and compared them to another series of

cephalograms without steel ball markers to check the accuracy of the sagittal and vertical

landmarks. Note that there was no steel ball markers were glued on the landmarks which

represented the molar superius mesial cusp (Msc), molar inferius mesial cusp (Mic), and

molar inferius (Mi), due to the overlapping right and left images on the cephalograms.

Tng found no significant differences between the two series of cephalograms for sagittal

and vertical landmarks. Thus, Pancherz’ method of analyzing the sagittal and vertical

landmarks on a cephalogram can be considered accurate. 93

Comparison of All Groups

For this study, the design of the appliance, anchorage device, treatment time,

force magnitude and direction were standardized in order to minimize the number of

variables to be interpreted when reviewing the data. Maxillary protraction was initiated

on patients between the ages of 6 years 1 month to 10 years 1 month in this study.

Takada79 has shown that forward maxillary displacement with protraction is more

favorable before or during acceleration of a child’s pubertal growth spurt.

72

Thus, the authors of this study reviewed the cervical vertebral maturation level in

all treated and control group patients in order to assess the patient’s skeletal age and to

account for differences in treatment outcome that may be due to the pubertal growth

spurt. The cervical maturation assessment used in this study was based on the new

Cervical Vertebral Maturation (CVM) method developed and employed by Baccetti,

Franchi, and McNamara.90 There were no statistically significant differences among any

of the three groups (i.e., Double-hinged, Hyrax, and Control groups). Baik94 reported

similar findings in that there were no statistical significant differences among the 47

subjects treated with rapid palatal expansion and protraction were divided into the

following age groups: (1) less than ten years old; (2) between ten and 12 years; and (3)

12 years or older.

Statistically significant differences between the treated groups and control group

were found in 12 of the 24 variables, as illustrated in Table 23. Majority of the

significant changes in this study were found in the sagittal measurement variables of the

treated groups which include OLp- A pt., OLp-B pt., OLp-Pg, Ii/OLp, Overjet, Mi/OLp,

and Molar Relationship.

Haas has demonstrated that maxillary expansion alone to can produce a slight

forward movement of point “A” along with a slight downward and forward movement of

the maxilla.15 Furthermore, because the maxilla is articulated with nine other bones of the

craniofacial complex palatal expansion can help to initiate a cellular response which will

help to disarticulate the maxilla from the craniofacial complex.2 This will in turn ease

maxillary protraction.

73

The benefits of using rapid palatal expansion in conjunction with protraction were

also reported in other studies. Ngan et al.95 reported 2.3 mm change with respect to “A”

point in 20 Class III patients who were treated with rapid palatal expansion and

protraction facemask for an average of six months. Similarly, Baik94 found 2.0 mm

forward movement of “A” point in a sample of 47 subjects who were treated with rapid

palatal expansion and protraction for a period of six months. Liou and Tsai1 were able to

attain a stable overall 5.8 ± 2.3 mm forward movement of “A” point through the use of an

alternating rapid maxillary expansions and constrictions (Alt-RAMEC) protocol along

with the use of a Double-hinged expander. Liou and Tsai attribute this success to the fact

that the Alt-RAMEC group experienced “an orthopedic process of sutural

expansion/protraction osteogenesis, which is similar, but less vigorous, than sutural

distraction osteogenesis.” 1,2

In this study, the Hyrax and Double-hinged expander groups had significant

forward movement of “A” point; however, only the Hyrax expander group was

significantly different when compared to the control group. The Hyrax expander group

had an average of +2.57 mm advancement of “A” point, but the Double-hinged expander

group had only +1.78 mm advancement of “A” point possibly due to the fact that the

Double-hinged expander subjects reported only wearing the protraction facemask for a

period of 8-10 hours. Nanda77 and Ishii et al 9 have reported similar “A” point changes of

1.5 mm and 2.1 mm, respectively, following treatment with maxillary protraction and

chincup therapy. Note that previous studies have found that the use of the chincup does

not affect the anteroposterior growth of the maxilla.55,67

74

However, treatment using protraction facemask therapy could cause counter-

clockwise rotation of the palatal plane and extrusion of the maxillary molar which in turn

may result in a downward and backward rotation of the mandible.9,12,17-19,71,94-97 This is a

possible explanation for the skeletal changes seen in the control group where the position

of the mandibular base (OLp-B pt.) and chin (OLp – Pg) showed significant forward

movement whereas the treated groups did not.

Dentally, the Double-hinged expander group showed significant changes in all

measurement variables but only had significant differences in four of the six

measurement variables when compared to the control group. The Double-hinged

expander subjects had a significant change of -1.95 mm in the position of the mandibular

incisor (Ii/OLp) as opposed to that of the control group’s significant change of +1.83

mm. As previously mentioned, the control group’s mandible continued forward growth

contributed to the significant difference from the treated groups whose mandibles moved

downward and backward as a result of treatment.

After accounting for mandibular skeletal and dental changes, the overjet

correction in the treatment groups was not as much as shown in the initial results.

Interestingly, the Double-hinged expansion group showed a significant mean change of

+5.22 mm overjet correction but actually only had +0.13 mm of overjet correction. The

Hyrax expansion group’s significant change of +4.68 mm was actually +2.48 mm in

overall overjet correction, which was more than the Double-hinged expansion group.

This could be because the Hyrax expansion group had a more forward movement of “A”

point and the Double-hinged expansion group had a more backward movement of the

mandible.

75

The position of the mandibular molar (Mi/OLp) in the Double-hinged expander

group significantly differs that of the Hyrax expander group as well as that of the control

group. This is due to the greater mandibular backward movement in the Double-hinged

group. Again, when discussing the amount of molar correction, the skeletal and dental

changes are taken into consideration because the downward and backward movement of

the mandible will change the position of the measuring points associated with the sagittal

variables OLp-Pg, Ii/OLp, and Mi/OLp, making them more negative.

The initial results show that the Double-hinged expander patients had +3.35 mm

molar relationship correction and the Hyrax expander patients had +2.30 mm correction.

However, after calculations were performed as described in Table 12, the amount of

molar correction was +0.61 mm in the Double-hinged expander group and -0.34 mm in

the Hyrax expander group. The greater molar correction in the Double-hinged expander

group is possibly due to the significant backward movement of the mandibular molar

related to the greater amount of downward and backward rotation of the mandible as

compared to the Hyrax expander group.

Moreover, the treatment effect of maxillary expansion and protraction facemask

therapy can only be appreciated once the changes related to growth have been taken into

consideration. Figures 9 and 10 show the overall sagittal differences between the treated

and control group for T2 – T1 and t2 – t1, respectively. Once growth is accounted for,

the Double-hinged expander group actually had a decrease in overjet by -1.88 mm as

compared to the Hyrax expander group’s increase of +0.47 mm. The treatment effect

with regards to molar relationship correction was -0.94 mm for the Double-hinged

expander patients and -1.89 mm for the Hyrax expander patients. This shows that growth

76

can negatively affect the results of any correction that is attained through treatment using

maxillary expansion and protraction facemask. Therefore, it is wise to consider over-

correcting the malocclusion in order to anticipate any potential changes due to growth.

Furthermore, it is important to keep in mind that the interpretation of any

treatment changes involving the incisors and molars could be inaccurate due to the

overlapping of the right and left images on cephalogram and due to the difficulty in

identifying the mesial contact point of the upper molars that have bands on them.

Although, bisecting of the right and left images were used in this study with consistency,

results must be interpreted with care. This is especially true when interpreting the

vertical dental changes due to transition between the deciduous and permanent dentition.

Of the seven vertical measurement points only N-A pt., Is – NL, and Overbite had

significant changes. The Double-hinged expander group was significantly different from

the control group, which had a significant vertical change of +2.16 mm in the maxillary

incisor position (Is – NL). A possible explanation is that the Double-hinged expander

subjects experienced incisor proclination of +5.5o as opposed to the control group’s

incisor proclination of 0.17 o. This may have been due to the difference in the design of

the expander. The Double-hinged expander has a lingual bar that extends forward and

touches the maxillary incisors’ cingulum area.

When compared to the control group, only the Hyrax expander group had

significant differences with respect to the variables N-A pt. and overbite. In fact, the

control group had a significant change in N-A pt (+1.63 mm). The Hyrax expander

group had a minimal (+0.10 mm) downward movement of “A” point relative to Nasion.

It can be concluded from this data that the Hyrax expansion group experienced more

77

forward movement and less downward movement of the maxilla, which is the opposite

pattern for the control group.

In addition, the Hyrax expansion group had a significantly different overbite than

the control group. In fact, the Hyrax expander group had an openbite of 1.25 mm;

whereas the control group had a significant increase 1.88 mm in terms of an underbite. It

is interesting to note that the Double-hinged expander patients did not experience a

significant change in overbite (mean change of -0.13mm). The protraction of the maxilla

in combination with the significant vertical eruption of the maxillary and mandibular

molars (Msc – NL and Mic –ML), may have contributed to the openbite seen in the

Hyrax expansion group. There were no significant changes in Msc –NL and Mic – ML

in the Double-hinged group.

Baik94 reported 1.6 mm of maxillary molar extrusion and 1.7 mm of mandibular

molar extrusion when a banded type rapid palatal expander was used in connection with

protraction facemask over a period of six months. However, protraction treatment

without expansion can also result in molar extrusion as noted by Takada 79, who found

significant molar extrusion greater than 1.8mm in patients who were pre- and mid-

pubertal stage.

Treatment was performed for nine months with the use of maxillary expansion at

the start and then protraction facemask therapy after expansion was completed. Typically

protraction of the maxillary arch will cause an anterior rotation and forward movement of

the maxilla unless a downward vector of protraction force was also used, as shown by

Hata et al. 98 This was related to the point of force application on the maxilla. In the

present study, protraction of the maxilla at the maxillary canine region with 30o

78

downward vector within a period of six months of protraction facemask therapy did not

produce a significant change in the palatal plane.

The significant changes were evident in the SNA measurements. In reference to

the cranial base, the protraction facemask therapy helped to displace the maxilla forward

by an average of 1.44o change in SNA for the Double-hinged expander group and by an

average of 2.06o change in SNA for the Hyrax expander group. Other investigators listed

in Table 25 have found similar mean increase in SNA that range from 0.3 to 2.2 degrees.

Table 25. Mean Change in SNA Following Protraction Facemask Therapy

References Mean change in SNA

Wisth et al.78, 1987 0.3 o

Tinlund99, 1989 2.5 o

Ngan et al.71, 1996 1.3 o

MacDonald97, 1999 2.31 o

Turley100, 2002 2.35 o

Wisth et al 78 studied 22 subjects with anterior crossbites who were treated for

three to 12 months with a quad-helix and protraction facemask therapy, and the quad-

helix was used for expansion only in children with anterior crossbite. The authors

reported that the there were no significant forward displacement of the maxilla following

protraction facemask therapy when comparing the treatment group to control group.

However, in this study the treated groups had significant change in SNA as compared to

the control group, which may an effect of orthopedic rapid palatal expansion prior to

protraction therapy.

79

Significant differences were present with regards to the ANB angle when

comparing the treated groups to the control group. The large increase of 2.57 o in the

Double-hinged expander group and a dramatic increase of 3.61o in the Hyrax expander

group occurred after six months of protraction facemask therapy. The significant

increase in ANB angle is the result forward movement of the maxilla and the downward

and backward rotation of the mandible.

Despite the significant change in Lop - B pt and OLp - Pg due to downward and

backward rotation of the mandible, the lower anterior facial height (ANS-Me) did not

significantly increase.

Clinical Relevance.

It can be concluded from the data gathered in this study that treatment of a

skeletal Class III malocclusion at an early age when maxillary suture has not interlocked

can be beneficial to the patient. Clinically both treatment groups showed improvement to

the Class III malocclusion as compared to the control group. The Hyrax expander group

appeared to have had a little more success possibly due to the fact that the Double-hinged

expander patients’ lack of compliance with regards to wearing the facemask for a

requested period of 14-16 hours. The only statistically significant difference between the

Double-hinged expansion group and the Hyrax expansion group, however, is related to

the mandibular molar position (Mi/OLp) in which the Double-hinged expander group had

a -1.25 mm movement and the Hyrax expander group had a +1.10 mm movement. This

was because the Hyrax expander group had more vertical and mesial molar movement

than the Double-hinged expander group. Hence, the Hyrax expander group also

experienced more of an openbite than the Double-hinged expander group.

80

A bonded type expander has the potential to reduce the tendency of posterior teeth

extrusion, which has been observed when using the banded expanders. 101 In addition,

there have been less vertical changes reported with bonded expanders as compared to the

banded expanders, possibly because of the splinting effect as well as the occlusal bite-

plate effect of the bonded expander. Therefore, it may be a good preventive measure to

use bonded rapid palatal expander and protraction facemask therapy on patients who

present with a Skeletal Class III openbite tendency.

Consequences if Early Treatment is Not Rendered.

The following lists the morphologic and functional changes that may occur if the

Class III malocclusion is not treated early: increased loading of the teeth; disturbances in

the functional equilibrium; impairment of the functions of chewing and speech, and even

difficulties in prosthetic reconstruction.37 Other effects of delayed treatment of Class III

malocclusions include psychosocial factors such as negative self-esteem and lower self-

confidence. Finally, the lack of early intervention for Class III patients will increase the

likelihood of the need for orthognathic intervention at a later stage.9

Individuality of Treatment Response.

From this study, it can be concluded that success and failure of orthopedic

treatment of children with skeletal Class III malocclusion is substantially dependent on

the patient’s compliance and the patient’s growth potential. As observed, the Double-

hinged expansion patients did not attain as much overjet correction as the Hyrax

expansion patient, primarily due to the fact that the Double-hinged expansion patients

reported only wearing the facemask for an average of 8-10 hours. However, it should be

noted that the Double-hinged expansion patients showed marked improvement to the

Class III malocclusion within the first few months of protraction.

81

Furthermore, once growth was taken into consideration and subtracted from the

treatment results to get the true amount of treatment effect, it was found that there was

minimal change to overjet and molar correction. Therefore, one should consider over-

correcting the Class III malocclusion in order to anticipate any potential changes due to

growth.

82

CHAPTER V

SUMMARY

The purpose of this study is to evaluate the quantitative difference, if any,

between the conventional protraction technique using the traditional Hyrax expander and

the alternative protraction protocol with the Double-hinged expander as advocated by

Liou.1 The differences between the two techniques were evaluated on lateral

cephalometric radiographs, in which the skeletal and dental changes with maxillary

expansion and protraction were measured.

Both treatment groups experienced statistically significant sagittal changes as

compared to the control group. But the primary reason for the improvement of the Class

III malocclusion is related to the downward and backward rotation of the mandible. The

Hyrax expansion group had more “A” point forward movement, but the success may

have been attributed to the higher level of compliance in this group compared to the

Double-hinged expansion group. Future studies reviewing the length of time that

protraction forces are placed on the maxilla can help to clarify the results of protraction

facemask therapy. Finally, long-term follow-up studies are needed in order to evaluate

the stability of this treatment modality.

83

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91

APPENDICES

APPENDICES

92

APPENDIX A

Intraclass Correlation Coefficient of Reliability for Sagittal Measurements

Variable Name

Time

Reliability

Skeletal OLp – A pt. T1 0.98979 OLp – B pt. T1 0.99929 OLp - Pg T1 0.99981 Dental Is / OLp T1 0.99874 Ii/ OLp T1 0.99859 Overjet T1 0.98737 Ms/OLp T1 0.99982 Mi/OLp T1 0.99983 Molar Relationship T1 0.99819 Skeletal OLp – A pt. T2 0.99649 OLp – B pt. T2 0.99856 OLp - Pg T2 0.99650 Dental Is / OLp T2 0.99943 Ii/ OLp T2 0.99896 Overjet T2 0.99490 Ms/OLp T2 0.99861 Mi/OLp T2 0.99945 Molar Relationship T2 0.93338

93

APPENDIX B

Intraclass Correlation Coefficient of Reliability for Vertical Measurements

Variable Name

Time

Reliability

Skeletal N - A pt T1 0.99941 ANS - Me T1 0.99920

Dental Is - NL T1 0.99560 Ii - ML T1 0.99933 Overbite T1 0.99489 Msc - NL T1 0.98518 Mic - ML T1 0.99934

Skeletal

N - A pt T2 0.99874 ANS - Me T2 0.99754

Dental Is - NL T2 0.99563 Ii - ML T2 0.99780 Overbite T2 0.99960 Msc - NL T2 0.99346 Mic - ML T2 0.99832

94

APPENDIX C

Intraclass Correlation Coefficient of Reliability for Angular Measurements

Variable Name

Time

Reliability

Skeletal SNA T1 0.99183 SNB T1 0.99036 ANB T1 0.99754 SNL - ML T1 0.99991 SNL - OLs T1 0.99854 SNL - NL T1 0.88566

Dental Is / SNL T1 0.99993 Ii / ML T1 0.89261

Skeletal

SNA T2 0.99575

SNB T2 0.99527 ANB T2 0.99552 SNL - ML T2 0.99136 SNL - OLs T2 0.99732 SNL - NL T2 0.99553

Dental Is / SNL T2 0.99964 Ii / ML T2 0.99394

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APPENDIX D

Intraclass Correlation Coefficient of Reliability for Superimpositions

Variable Name

Time Reliability

Skeletal OLp – A pt. T2 – T1 0.81099 OLp – B pt. T2 – T1 0.83303 OLp – Pg T2 – T1 0.83192 Dental Is / OLp T2 – T1 0.98587 Ii/ OLp T2 – T1 0.98526 Overjet T2 – T1 0.95158 Ms/OLp T2 – T1 0.98521 Mi/OLp T2 – T1 0.93664 Molar Relationship T2 – T1 0.96216 Skeletal N - A pt T2 – T1 0.97030 ANS – Me T2 – T1 0.98788 Dental Is – NL T2 – T1 0.95383 Ii – ML T2 – T1 0.94953 Overbite T2 – T1 0.99568 Msc – NL T2 – T1 0.89454 Mic – ML T2 – T1 0.99221 Skeletal SNA T2 – T1 0.95158 SNB T2 – T1 0.9759 ANB T2 – T1 0.96112 SNL – ML T2 – T1 0.99405 SNL – OLs T2 – T1 0.98337 SNL – NL T2 – T1 0.97119 Dental Is / SNL T2 – T1 0.99357 Ii / ML T2 – T1 0.92210

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APPENDIX E

Error of Sagittal Measurements Variables (mm)

T1

T2

Sagittal Min Max Mean S.D. Min Max Mean S.D. Skeletal 1. OLp – A pt. 69.76 83.22 77.88 3.86 72.11 83.82 79.70 3.58 2. OLp – B pt. 79.97 92.10 85.12 3.71 79.54 91.28 83.75 3.66 3. OLp – Pg 81.59 95.00 87.19 4.13 79.44 95.57 86.13 4.87 Dental 4. Is/OLp 75.56 90.86 83.89 4.57 80.74 94.99 87.19 3.89 5. Ii/ OLp 79.77 91.25 84.64 3.28 78.96 90.27 82.77 3.39 6. Overjet -4.22 3.75 -0.76 2.38 0.51 6.96 4.43 2.02 7. Ms/OLp 44.78 57.90 52.97 4.05 46.06 61.95 54.99 4.67 8. Mi/OLp 49.35 64.83 56.86 4.65 49.03 63.21 55.52 4.37 9. Molar Rel. -7.97 0.31 -3.89 2.73 -3.00 4.41 -0.53 2.27 Sagittal Min Max Mean S.D. Min Max Mean S.D. Skeletal 1. OLp – A pt. 62.66 70.45 67.65 2.92 66.03 73.59 70.49 2.95 2. OLp – B pt. 71.49 85.75 76.72 4.33 69.71 82.28 75.55 4.10 3. OLp – Pg 71.82 87.75 78.29 4.71 70.98 83.83 77.30 4.22 Dental 4. Is/OLp 71.30 77.73 74.97 2.57 74.07 84.61 79.49 3.58 5. Ii/ OLp 74.40 80.59 77.74 2.73 70.04 80.96 75.98 4.42 6. Overjet -4.06 -1.63 -2.77 0.98 1.24 7.18 3.51 1.88 7. Ms/OLp 40.67 59.53 48.52 5.79 46.33 65.57 52.41 6.08 8. Mi/OLp 45.76 65.19 51.65 6.35 45.24 65.16 52.41 6.59 9. Molar Rel. -6.90 -1.00 -3.12 2.08 -2.77 1.09 0.01 1.11 Sagittal Min Max Mean S.D. Min Max Mean S.D. Skeletal 1. OLp – A pt. 65.62 74.89 69.37 2.95 66.84 75.31 69.93 2.49 2. OLp – B pt. 70.76 88.05 76.73 5.97 72.92 89.40 78.22 6.02 3. OLp – Pg 71.43 90.00 78.35 6.49 73.28 91.51 80.31 7.04 Dental 4. Is/OLp 71.63 83.72 75.12 3.97 71.51 85.47 76.34 4.73 5. Ii/ OLp 73.83 86.13 77.77 4.38 74.18 87.80 79.51 4.67 6. Overjet -4.56 -1.87 -2.67 0.88 -4.62 -2.34 -3.17 0.68 7. Ms/OLp 42.63 56.57 47.87 5.32 44.88 58.09 49.38 5.16 8. Mi/OLp 43.90 61.99 50.92 6.38 47.48 63.81 52.96 6.40 9. Molar Rel. -7.45 -0.04 -3.05 2.46 -8.48 -1.21 -3.58 2.30

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APPENDIX F

Error of Vertical Measurements Variables (mm)

T1

T2

Vertical Min Max Mean S.D. Min Max Mean S.D. Skeletal 10. N-A pt. 49.84 63.02 55.51 4.17 49.18 64.03 55.96 4.55 11. ANS – Me 61.19 75.90 67.08 4.69 64.04 77.49 68.62 3.92 Dental 12. Is – NL 25.39 31.90 27.66 2.13 24.95 30.63 27.42 1.89 13. Ii – ML 35.84 42.07 38.76 2.58 37.76 43.95 40.74 2.18 14. Overbite -0.76 4.96 2.03 2.17 -2.07 5.46 2.02 2.38 15. Msc – NL 15.03 24.01 18.95 2.52 16.37 24.28 19.00 2.67 16. Mic – ML 24.67 34.09 29.45 2.74 25.08 32.10 30.08 2.25 Vertical Min Max Mean S.D. Min Max Mean S.D. Skeletal 10. N-A pt. 49.03 57.41 53.48 2.88 46.34 58.20 53.72 3.50 11. ANS – Me 57.44 62.68 60.50 1.68 59.74 69.07 63.57 3.19 Dental 12. Is – NL 21.63 27.87 25.78 1.86 23.07 27.80 26.24 1.65 13. Ii – ML 35.02 39.87 37.51 1.65 36.88 41.53 39.07 1.21 14. Overbite -0.78 9.46 3.41 3.42 0.36 4.06 2.22 1.44 15. Msc – NL 15.47 21.09 18.48 1.86 17.88 21.84 19.77 1.51 16. Mic – ML 25.45 31.13 28.04 2.02 26.33 32.18 29.42 1.66 Vertical Min Max Mean S.D. Min Max Mean S.D. Skeletal 10. N-A pt. 49.11 55.22 52.67 2.43 50.83 57.38 54.42 2.17 11. ANS – Me 55.27 70.03 61.25 5.31 58.49 70.22 63.23 5.03 Dental 12. Is – NL 19.57 30.18 23.88 3.58 20.92 31.56 26.07 3.42 13. Ii – ML 37.33 43.16 40.37 2.24 37.96 44.94 41.88 2.44 14. Overbite 1.79 7.02 3.46 1.84 3.72 7.33 5.25 1.56 15. Msc – NL 13.24 21.75 17.24 2.81 15.66 21.54 18.84 2.10 16. Mic – ML 26.51 31.93 29.60 1.70 27.71 33.92 30.59 2.14

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APPENDIX G

Error of Angular Measurements Variables (o)

T1

T2

Angular Min Max Mean S.D. Min Max Mean S.D. Skeletal 17. SNA 72.5 82.5 79.3 3.0 75.3 88.6 80.8 3.6 18. SNB 73.0 81.75 79.2 2.6 72.0 81.3 78.1 3.1 19. ANB -3.4 3.8 0.1 2.4 -1.5 7.6 2.7 3.1 20. SNL - ML 29.8 38 35.0 2.8 27.8 39.3 36.5 3.6 21. SNL - OLs 15.0 26.5 21.0 3.9 14 26.5 19.8 5.2 22. SNL - NL 1.8 11.5 5.7 3.1 1.3 9.5 5.9 2.8 Dental 23. Is/ SNL 83.3 116 98.8 12.5 90.3 117.5 104.1 10.1 24. Ii /ML 72 94 84.8 6.7 75.5 91.5 83.4 5.4 Angular Min Max Mean S.D. Min Max Mean S.D. Skeletal 17. SNA 76.3 83.0 79.3 2.8 78.0 86.8 81.7 3.2 18. SNB 77.0 85.5 80.3 2.8 76.5 82.3 78.9 1.9 19. ANB -5.5 3.0 -1.0 2.7 1.0 4.8 2.8 1.5 20. SNL - ML 32.3 40.3 36.3 2.6 34.8 41.8 38.0 2.2 21. SNL - OLs 15.3 29.0 23.3 4.1 15.5 25.3 21.2 2.8 22. SNL - NL 1.8 12.0 8.3 3.2 2.5 10.8 7.3 2.6 Dental 23. Is/ SNL 91.5 121 104.3 8.8 98.5 117 109 5.5 24. Ii /ML 73 106.3 91.1 10.4 75.8 105.3 87.9 11.4 Angular Min Max Mean S.D. Min Max Mean S.D. Skeletal 17. SNA 75.0 83.5 79.8 3.3 74.3 84 79.7 3.8 18. SNB 75.5 85.3 79.8 2.9 76.5 86.3 79.8 3.0 19. ANB -3.0 3.0 0.1 2.2 -3.0 4.8 -0.1 3.0 20. SNL - ML 31.8 42 36.4 3.5 31 40.8 36.2 4.2 21. SNL - OLs 17 27.8 21.4 3.9 15.3 29.3 22.5 5.4 22. SNL - NL 3.5 12.0 8.1 3.1 3.8 12.3 7.9 2.6 Dental 23. Is/ SNL 96.0 107.5 101.1 4.9 89.5 112.3 101.0 9.5 24. Ii /ML 81.3 95.0 89.0 3.6 81.0 100.0 88.9 7.9

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APPENDIX H

Error of Superimpositions

Variable Name Time Min Max Mean Difference

S.D.

Skeletal OLp – A pt. T2 – T1 1.14 1.87 -0.46 0.66 OLp – B pt. T2 – T1 -1.10 -0.66 -0.04 0.17 OLp - Pg T2 – T1 -0.70 -0.45 -0.28 0.32 Dental Is / OLp T2 – T1 3.41 3.62 -0.21 0.18 Ii/ OLp T2 – T1 -1.24 -1.18 -0.07 0.07 Overjet T2 – T1 4.58 4.86 -0.15 0.16 Ms/OLp T2 – T1 1.94 2.04 -0.15 0.16 Mi/OLp T2 – T1 -1.38 -0.87 -0.13 0.25 Molar Relationship T2 – T1 2.81 3.43 -0.02 0.26 Skeletal N - A pt T2 – T1 0.64 1.51 -0.05 0.23 ANS - Me T2 – T1 2.46 3.21 0.13 0.22 Dental Is – NL T2 – T1 -0.15 0.08 -0.25 0.15 Ii – ML T2 – T1 1.86 1.90 0.24 0.13 Overbite T2 – T1 -0.11 0.44 0.21 0.13 Msc - NL T2 – T1 -0.65 1.11 -0.24 0.50 Mic - ML T2 – T1 0.05 0.29 0.16 0.14 Skeletal SNA T2 – T1 0.8 1.5 0.6 0.24 SNB T2 – T1 -1.5 -0.7 -0.3 0.37 ANB T2 – T1 2.2 2.3 0.9 0.19 SNL - ML T2 – T1 1.1 1.3 -0.4 0.35 SNL - OLs T2 – T1 -2.8 -1.9 -0.6 0.41 SNL - NL T2 – T1 -1.5 -1.3 0.3 0.29 Dental Is / SNL T2 – T1 5.2 6.7 -0.5 0.16 Ii / ML T2 – T1 -3.3 -1.3 -1.5 2.26

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effective maxillary protraction: hyrax expansion appliance

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